Biology Notes Modules 1-4 PDF

Biology; Preliminary Notes Syllabus Module 1: Cells as the Basis of Life What distinguishes one cell from another? How do cells coordinate activities within their internal environment and the external environment? Module 2: Organisation Of Living Things How are cells arranged in a multicellular organism? What is the difference in nutrient and gas requirements between autotrophs and heterotrophs? How does the composition of the transport medium change as it moves around an organism? Module 3: Biological Diversity How do environmental pressures promote a change in species diversity and abundance? How do adaptations increase the organism’s ability to survive? What is the relationship between evolution and biodiversity? What is the evidence that supports the Theory of Evolution by Natural Selection? Module 4: Ecosystem Dynamics What effect can one species have on the other species in a community? How do selection pressures within an ecosystem inﬂuence evolutionary change? How can human activity impact an ecosystem? 1.1 What Distinguishes one cell from another? Cell Theory - All living things are made of cells - Cells are the basic structural and functional units of organisms - All cells come from pre-existing cells Types of Organism Unicellular - Are made of only one cell - Include bacteria, protozoa, unicellular algae and unicellular fungi or yeasts - They are the oldest forms of life and they existed 3.8 billion years ago - Engulf food particles-phagocytosis\ Multicellular Organisms - Are made up of more than one cell eg humans, dogs - The cells coordinate with each other in order to regulate the various functions of the body - Different cells in a multicellular organism may be the nerve cells, skin cells, blood cells, bone cells Cell Structure- Classiﬁcation of cells Prokaryotes (Unicellular Organisms) ○ Much smaller and simpler than eukaryotic cells ○ No membrane-bound organelles ○ Divided into two groups → Archaea and Bacteria ○ cell division by binary ﬁssion ○ Four Main Structures Cell membrane Cytoplasm Ribosomes Genetic Material → Found in a large loop called the nucleoid. Eukaryotes (Unicellular and Multicellular) More complex and large than prokaryotes Approx. 10-100um. Multicellular plants and animals are composed of a variety of different types of eukaryotic cells. Divided into kingdoms → Plants, Fungi, Protist and Animals cv cell division by mitosis Similarities DNA Cell membrane (controls what goes in and out of cells) Ribosomes Cytoplasm (what all the organelles sit in) Organelles Name Structure Function animal/plant/both Cytoplasm Consists of a liquid-based background, in both which there are dissolved chemical substances e.g. ions such as chloride ions The cytoplasm is responsible for holding the components of the cell and protects them from damage. It stores the molecules required for cellular processes and is also responsible for giving the cell its shape. Nuclear It serves to separate the chromosomes from both membrane the rest of the cell. The nuclear membrane includes an array of small holes or pores that permit the passage of certain materials, such as nucleic acids and proteins, between the nucleus and cytoplasm. Nucleus The nucleus is a large spherical oval both structure in the cytoplasm. The nucleus is transparent and colourless. There are two main functions for a nucleus including; storing the cell’s DNA and being responsible for the growth of the cells, reproduction etc. The nucleus produces ribosomes. Colourless, transparent, jelly like. Contains the genetic information of a cell. The information in chromosomes is used to control the develops and the functioning of the whole cells Ribosomes Ribosomes are a cell structure that assists both with making protein. Ribosomes are found ﬂoating around in the cytoplasm and/or attached to the rough endoplasmic reticulum. Chloroplast Chloroplasts are only found in plant cells. plants Photosynthesis occurs in this section of the cell. The chloroplast uses the sunlight to convert the energy into sugars to power the plant cells. Inside of the chloroplasts, there are little green chlorophylls (molecules). Golgi Bodies The golgi body is an organelle found in most both eukaryotic cells. There are numerous functions of the golgi such as sorting and processing proteins. They are also responsible for determining which proteins are allowed outside of the cell. They take in the ribosomes, a bit like a post ofﬁce. Lysosomes The main function of lysosomes is to digest both and remove waste from the cell. They contain digestive enzymes. They are the stomach of the cell. Lysosomes are surrounded by a layer of lipids acting as a membrane Mitochondria The mitochondria are the powerhouse of the Both cell. They produce the energy for the cell known as ATP through cellular respiration. Responsible for creating more than 90% of the energy needed to sustain life. Animals have more than plants. Plants only use their mitochondria at night. Cytoskeleton The cytoskeleton is present in all cells. They both are a complex network of interlinking ﬁlaments and tubules throughout the cytoplasm. They support shape and help facilitate movement. Centrioles These are found in pairs in animal cells, they Animal are involved in formation of the spindle for mitosis Cell Wall The cell wall provides support and protection plants for the cell. They are only found in plant cells. Cell walls lie on the outside of the cell membrane Cell The plasma membrane, or the cell both Membrane membrane, provides protection for a cell. It also provides a ﬁxed environment inside the cell, and that membrane has several different functions. One is to transport nutrients into the cell and also to transport toxic substances out of the cell. Sometimes called the plasma membrane, this is the organelle that surrounds the whole cell.. It is ﬂexible and holds all the contents of the cell. It regulates what goes in and out of the cell Rough The rough ER, studded with millions of both endoplasmic membrane bound ribosomes, is involved reticulum (ER) with the production, folding, quality control and despatch of some proteins. Smooth ER is Smooth largely associated with lipid (fat) endoplasmic manufacture and metabolism and steroid reticulum (ER) production hormone production. It also has a detoxiﬁcation function. The rough endoplasmic reticulum has on it ribosomes Vacuole Found only in plant cells, this sac-like Mostly plants and organelle is used as food storage for the some animals plant. It contains cell sap, which is made of water and dissolved substances such as sugars and salts. in some cells, takes up 80-90% of the cell volume A vacuole is a membrane-bound cell organelle. In animal cells, vacuoles are generally small and help sequester waste products. In plant cells, vacuoles help maintain water balance. Sometimes a single vacuole can take up most of the interior space of the plant cell. Technology Light microscopes: Produces images up to x1500 depending on the lenses (ours only go up to x400) Both living and non-living specimens can be viewed under a compound light microscope. A light source passes through a condenser lens then through the specimen. The beam of light passes through the convex objective lens, the image is magniﬁed and viewed through the ocular lens. Magniﬁcation of up to 1500 x and maximum resolution of 200 nm. Adv: inexpensive related to electron microscopes and can look and live samples Dis: Can't magnify more than 2000 Electron microscopes: Revolutionised the study of microscopic organisms. Uses an electron beam instead of light and electromagnets instead of glass lenses. Greater resolution due to shorter wavelength. Many cell parts were seen for the ﬁrst time after the invention of the electron microscope. Two types: Transmission Electron Microscope (TEM) Electrons pass through the specimen. Produces 2D images. Most common form of electron microscope. Maximum magniﬁcation = 1 500 000x Resolution = 2nm Dis: Electron microscopes are sensitive to vibration and electromagnetic ﬁelds and must be housed in an area that isolates them from possible exposure. And hard to maintain Adv: TEMs offer the most powerful magniﬁcation, potentially over one million times or more. images are high-quality and detailed Scanning Electron Microscope (SEM) Bombards solid specimens with a beam of electrons. The electron beam does not pass through the specimen, but it is scattered from it. Resolution = 10nm Produces 3D images. Dis: SEMs are expensive, large and must be housed in an area free of any possible electric, magnetic or vibration interference. Hard to maintain. Adv: The quality is really good. The resolution of electron microscopy images is in the range of up to 0.2 nm, which is 1000x more detailed than light microscopy. FLUORESCENCE MICROSCOPES: Better resolution than light microscopes. Sample is labelled with a ﬂuorescent dye that attaches to particular structures. Sample is illuminated with a high-intensity source of light that causes the ﬂuorescent substance to emit light. Adv: Superior image clarity over ﬂuorescence microscope, Can provide a composite 3D image of the sample Dis: Unable to produce high deﬁnition images of SUVs or oligo lamellar liposomes Organelles visible with a Light Microscope Organelles visible with an Electron Microscope Nucleus (can be stained) The cell membrane (need staining) Cytoplasm (will need staining) Cell wall Cell wall Golgi (need staining) Chloroplasts Chloroplast Vacuole (plant cells only) Mitochondria ER (need staining) Ribosome Lysosomes Cytoplasm (need staining) Centrosomes Cytoskeleton (need staining) Conversions Conversion factor: 1mm = * 1000 * µm(micrometre) 1 µm = * 1000 * nm(micrometre) Scale: Actual size / size of drawing Example 1: Actual diameter = 60µm Diameter of cell drawn = 5cm Scale = 60/5 → 12µm - 1cm Magniﬁcation = Image size/Actual size Example 1: Organelles = 7µm Actual size = 5cm → 50mm → 50 000µm Magniﬁcation = 50 000/ 7 = 7152.9x (1 d.p) Example 1: Example 2: Sample: cheek cells Magniﬁcation = 400X (10x eyepiece, 40x objective) Diameter of FOV = 440 µm Number of whole cells across FOV = 6 Cell size = (440 µm)/6=73 µm Fluid mosaic model: Cell membrane: - Membrane is extremely thin just two molecules thick - The cell membrane controls the exchange of material between the internal and external environments of the cell. - It is selectively permeable meaning only certain molecules or ions are allowed in or out. - Cell membrane is permeable to small molecules and lipid-soluble molecules due to phospholipids being made of lipids - The cell membrane is also involved in cell recognition and communication with other cells. Fluid mosaic model: - Cell membranes consist of a bilayer (two layers) of phospholipid molecules. - Phospholipid molecules have a hydrophilic (water-attracting) ‘head’ and two hydrophobic (water-repelling) ‘tails’. - The hydrophilic heads form the outside and inside lining of the cell membrane, and the hydrophobic tails of the two layers of phospholipids meet in the middle. - Other molecules, such as proteins, carbohydrates and cholesterol, are scattered throughout the bilayer. Visible using an electron microscope. TEM can show 2 layers of membrane Membrane Proteins Proteins are scattered or ﬂoat through out lipid bilayer Membrane proteins have various functions: 1. Transporters 2. Enzymes 3. Cell surface receptors 4. Cell surface identity markers 5. Cell-to-cell adhesion proteins 6. Attachments to the cytoskeleton Factors affecting the membrane: Cholesterol - Gives stability to the cell membrane without affecting the ﬂuidity. - Reduces the permeability of the cell membrane to small, water soluble molecules. Temperature - As temperature increases, ﬂuidity increases. - Phospholipids chrome less tightly packed and move more freely - As temperature decreases, cell membranes with a high percentage of saturated fatty acid may solidify Proteins - Some penetrate the whole way through the membrane, forming channels that allow some materials to pass through the membrane. - Receptor proteins cause the cells to respond only to signals from substances. - Carrier proteins can assist in facilitated diffusion or active transport (May require energy to go against the concentration gradient) 1.2 How do cells coordinate activities within their internal environment and the external environment? What is Membrane Permeability? - Permeability is the ability of a membrane to allow substances to pass through it - Permeability is; Impermeable: allows no molecules to pass through it, has no pores Selectively permeable: only allows certain molecules to pass through it, small pore - Permeable: allows all molecules to pass through it, large pores Remember: Solvent: is a substance able to dissolve other substances Solute: is a substance which dissolves in a solvent Example: Sugar (solute) is dissolved in water (solvent) to make a sugar solution Dilute solution: contains only a small amount of solute Concentrated solution: contains a large amount of solute What Determines the Movement of Molecules Across Cell Membranes? Permeability of a membrane to a molecule depends on the molecule’s Size: small molecules move fast Electrical charge: neutral molecules eg CO2 and O2 have high permeability but charged molecules do not Lipid solubility: molecules soluble in lipids move easily Thus the lipid nature of cell membranes makes them: ○ Permeable to small molecules and lipid soluble molecules that can move freely through the phospholipids ○ Impermeable to most water soluble molecules, ions (charged molecules) and polar molecules (charged regions but no overall charge). These substances must thus pass through speciﬁc protein channels in the membrane. How Do Molecules Move Across Cell Membranes? - Movement of materials in and out of cells is either passive or active. - Passive movement requires no energy and occurs via diffusion or osmosis - These processes occur when a concentration gradient is present. Particles move from where there are many to where there are fewer, (that is from a high to a lower concentration) and eventually become evenly distributed in the space. - No energy is required Diffusion What is Diffusion? - It is the movement of any type of molecule from a high to a low concentration until equilibrium is met - Both solute or solvent particles are free to move in diffusion - There is no barrier - Results in the number of molecules on both sides of the membrane are the same Simple Diffusion - May involve movement solid, liquid or gas molecules through another medium of solid, liquid or gas - Simple diffusion is deﬁned as the process in which a substance moves through a semipermeable membrane or in a solution without any help from transport proteins.. - There are 3 factors that can affect the rate of diffusion: - Concentration: The greater the difference in concentration gradient, the faster the rate of diffusion. - Temperature: - High temperature = High rate of diffusion - Low temperature = Slow rate of diffusion - Particle size: - Small particle = fast rate of diffusion - Big particles = slow rate of diffusion Facilitated Diffusion - Similar to simple diffusion - Occur through transport proteins - Movement of the molecules is assisted by carrier proteins or channel proteins which are speciﬁc to one or several similar solutes - Used by some larger molecules (glucose, amino acids) and electrically charged molecules (sodium, chloride ions) as simple diffusion is too slow to meet cell needs. - It is speciﬁc, passive and saturates when all carriers are occupied How Does the Protein Act? - The protein may act as a channel protein or a carrier protein - Channel protein spans the cell membrane and allows direct passage from one side to the other; they have open and closed states controlled by electrical or physical signals. - Carrier proteins bind with a molecule and then changes shape to enable them to move the molecule to the other side Osmosis A process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one. Isotonic Solution - solute concentration inside = solute concentration outside - water molecules move in and out of cell freely cells stay normal Hypotonic Solution - solute concentration inside > solute concentration outside - water molecules move into the cell - cells swell Hypertonic Solution - solute concentration inside < solute concentration outside - water molecules move out of the cell - cells shrink Surface Area to Volume Surface area (SA) cell is the area of the outside surface Volume (V) of a cell is the amount of space inside the cell or its inside capacity SA:V ratio is dependent on the size and shape of the cell A cell needs enough surface area to supply its volume with requirements and remove wastes. Small cells: - A smaller cell has more surface area in relation to its volume and so a higher SA:V Large cells: - A large cell has a smaller surface are in relation to its volume and so a lower SA:V Enzyme - protein molecules that control all the chemical processes of living systems - produced within living cells - Intracellular or extracellular - organic catalysts, also known as biological catalysts - responsible for increasing the rate of reactions that occur in living organisms, without enzymes metabolism would be so slow at body temperature that insufﬁcient energy would be available to maintain life Catalysts - is a general term for any substance that speeds up or brings about a chemical change - remain unchanged at the end of a reaction - can be reused - enable reactions to occur at lower temperatures, thus body temperatures do not need to be so high Composition of enzyme - Enzymes are globular proteins as they consist of long chains of amino acids that have been folded into a speciﬁc shape. - Each enzyme contains a speciﬁc active site and catalyses a distinct chemical reaction - The molecule on which an enzyme acts is called a substrate. - The interaction occurs between the enzyme’s active site and the substrate. Enzymes are substrate speciﬁc Simple model enzyme - One compound (or a very few compounds) can react with a particular enzyme, this is speciﬁcity - Each enzyme catalyses a distinct chemical reaction in which the compound/substrate are changed into other compounds - Enzymes are only required in minute amounts - Original model was lock (enzyme) and key (substrate) - Current model induced ﬁt Enzymes: - Enzymes are protein molecules that control all metabolic reactions in living cells. - Without them, chemical reactions in your body would be very slow. - They are catalysts (speed up the rate of reaction) - They control the rate of reactions - Enzymes are composed of protein molecules that are often highly folded to create a particular shape. - The surface of the enzymes with a speciﬁc shape is called the ‘active site’ which is where the reactants (substrates) in a chemical reaction bind to. - They are substrate speciﬁc Factors affecting enzymes: - Enzymes are temperature sensitive and function best at the body temperature of the organism in which they occur (usually 40°C) - Enzyme activity slows until it stops at its optimum level (the highest it can function) - At high temperatures the motion associated with heat energy can make the protein structure change the shape of the active site causing the enzyme to denature. Change is irreversible. - Excessive cold also causes the enzyme to change shape and its functioning to slow down or stop. This change is reversible. - Enzymes are pH sensitive - A catalyst increases the rate of reaction as temperature increases until the optimal temperature is reached The importance of shape in enzymes: - Enzymes are substrate speciﬁc. - Only particular enzymes can ﬁt each substrate. - Enzymes will denature (stop working) if there is change in pH value or temperature change. Photosynthesis: Carbon dioxide + water glucose → glucose + oxygen Chloroplast - Where light energy is converted to glucose (food) for the plant and oxygen is released - Chlorophyll found inside the chloroplast is green pigment that absorbs the energy from sunlight. Stage 1 : Light-dependent reactions - Chlorophyll captures solar energy and uses it to produce adenosine triphosphate (ATP) - Photolysis occurs ( water splits into H and 02 (g) Stage 2 : Light-independent reaction - Don't need light in this step - ATP from stage 1 provides energy - Combine CO with H - Produce glucose, water and adenosine diphosphate (ADP) - Takes place in the stroma Aerobic Respiration - Chain of at least 20 separate reactions each catalysed by a speciﬁc enzyme. - Basic formula: Cellular Respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O. Glucose + Oxygen → Carbon dioxide + Water + Energy Anaerobic Respiration - Environment has no oxygen eg bacteria or not sufﬁcient oxygen eg muscle cells - Use an anaerobic pathway in cytosol of cells - Use molecules other than oxygen - Alcohol fermentation used by yeasts, many bacteria and some plants - Lactic acid fermentation used by humans 2.1 How are cells arranged in a multicellular organism? Types of cells Unicellular - Contain one cell, either prokaryotic or eukaryotic - Includes bacteria, protozoa unicellular algae, and unicellular fungi or yeast - First forms of life - A single cell carries out all life processes → obtaining nutrients, exchanging gas, removing waste and reproduction - High SA:V ratio which allows for more efﬁcient movement of substances - Requires a moist environments for diffusion and osmosis to occur Colonial - A group of cells working or organism working collectively is called a colony - May be unicellular or multicellular - Can exist independently, however in a multicellular organism colonial organisms cannot exist alone. - Each cell or member of the colony function individually Multicellular - A community of cells working together to enable the organism to carry out life processes, including reproduction. - Composed of many different specialised cells, Similar cells are grouped together and perform speciﬁc functions that combine for the efﬁcient functioning for the organism - Consists of eukaryotic cells. - Large organisms made up of smaller cells increases SA:V ratio. - Each specialised cell type is structurally suited to a particular function. - ○ Embryonic cells develop suitable structural changes to best suit their function → Red blood cell - Groups of cells from tissue. Large multicellular organisms have tissues organised into organs and systems. Stem Cells are biological cells found in all multicellular organisms they can divide (through mitosis) and differentiate into diverse specialised cell types can self-renew to produce more stem cells There are two types: Embryonic Stem Cells - are pluripotent - can differentiate into all the specialised cells - gives rise to every cell type in a fully formed body - are in very low numbers in adults Adult Stem Cells - Are more specialised than embryonic stem cells, can generate different cell types for the speciﬁc tissue or organ in which they live - have been identiﬁed in many organs and tissues eg brain, bone marrow, peripheral blood, blood vessels, skin, teeth and are thought to reside in a speciﬁc area of each tissue. - replenish dying cells and regenerate damaged tissues eg new skin, muscle in adults Formation of specialised cells - When cells become specialised they differentiate – they develop structures enabling them to carry out their function, making them different to other cells. - Specialised cells originate from stem cells, which are undifferentiated cells with the ability to divide repeatedly. - Cell specialisation refers to the function of the cell, while differentiation is the process a stem cell goes through to become specialised. - Enables organisms to grow larger while still efﬁciently carrying out processes. - Specialised cells cannot survive independently – they rely on other cells in the organisms to carry out functions they cannot. - Communication between cells is vital. - In animals this is via the bloodstream and nervous system whereas in the plants it is brought about by chemical and physical contact between cells. 2.2- Nutrient and Gas Requirements Autotrophs - Produce their own organic compounds and energy from inorganic compounds from their environment, such as carbon dioxide, water and inorganic materials such as nitrates, phosphates and sulphates - Can be divided into two groups: - Photoautotrophs – use light energy (e.g. green plants). → Use energy from sunlight in process photosynthesis to make organic substances - Chemoautotrophs – use chemical energy (e.g. nitrifying bacteria in the soil) → Producers in the food chain or web: green plants and algae Heterotrophs - Rely on consuming other organism - Must have a supply of organic molecules - Obtain nutrients from their living environment - Consumers and decomposers in the food chain or web - Require systems that help them break down and absorb nutrients that they obtain by ingesting other living things - Include all animals and fungi Non Vascular plants - Non-vascular plants are plants without a vascular system consisting of xylem and phloem. Instead, they may possess simpler tissues that have specialized functions for the internal transport of water. Normally found in damp areas - Need a constant supply of water to live and reproduce and do not have vein like structures and must absorb water and nutrients through the surface of their leaves - Reproduce by spores in capsules (wild-dispersal) - Nutrients absorbed and waste removed by diffusion and osmosis Vascular Plants - Contain the organs: leaves, stem, roots, ﬂowers, seeds - Contain the systems: root, shoot, vascular system What is the Vascular System? - Vascular system is responsible for the transport and distribution organic compounds, water, minerals and gases around the plant - This system has 2 different types of tissue: - Xylem carry water and water soluble nutrients and minerals from the soil via the roots - Phloem is composed of thin-walled cells that transport sugars (dissolved sucrose) and other plant products from one part of a plant to another. Root System - The function of this system is to anchor the plant and absorb water and inorganic nutrients from the soil. Roots should be anchoring the plant and absorbing water and inorganic nutrients from the soil. - Very large surface area. - Epidermal cells in the roots are responsible for absorption of water and dissolved inorganic nutrients from the soil - The ﬂatten nature of these cells increases their exposed surface but as the surface area of general epidermal cells is smaller than root hairs, less water is absorbed per cell than in the root hair zone. - Water moves across the root tissues from outer epidermal layer to vascular stele in the centre of the root and into the xylem tissue - Water moves through the roost via osmosis - Mineral ions into the roots by diffusion, if concentration gradient too low facilitated diffusion or active transport - Root cells have no chloroplasts so no photosynthesis but carry out aerobic respiration where oxygen diffuses into the cells from air pockets in the soil and carbon dioxide diffuses out Shoot System (Stem) - Provides structural support and a transport pathway and is normally located above ground - Consists of 3 main functions - Dermal→ outer layer provides protection, waterprooﬁng and control of gas exchange - Vascular → Composed of the xylem and the phloem within vascular bundles - Ground Tissue → Fills in around vascular tissue Shoot System (Leaves) - Leaves are responsible for three important processes in plants: - Photosynthesis: absorb sunlight and carbon dioxide during the day, release oxygen, provide chlorophyll, to make and transport glucose - Transpiration: release water to cool the plant, suction pull to lift water from the roots to the top of the plant - Exchange of gases : release of excess oxygen from photosynthesis and the release of carbon dioxide as a result of respiration which is used for photosynthesis. Note cellular respiration occurs during the day and at night. - Leaves are arranged along the stems of plants in a way that exposes them to the maximum amount of sunlight possible. They are angled so that the sunlight strikes the upper surface of the leaves. - Thin, ﬂat structure of leaves is well suited to this function – no internal cell is too far from the light. Large SA allows maximum absorption. - Transparent epidermis allows sunlight to penetrate the photosynthetic cells beneath. - Outermost layer cells, epidermis is transparent to allow sun to reach photosynthetic cells inside Outermost Layer: Epidermis - Epidermis forms a single protective layer of cells on the upper and lower surfaces of the leaf. It is transparent, so sunlight can readily penetrate through to the photosynthetic cells within. - Epidermal cells secrete a waterproof cuticle which prevents evaporation of water. Contains guard cells that occur in pairs around the stoma (stomata) and these control exchange of gases and loss of water from leaves - Contains guard cells that occur in pairs around the stoma (stomata) and these control exchange of gases and loss of water from leaves Middle Layer: Mesophyll - These cells in the centre of the leaf consist of two types: - Palisade mesophyll cells are found most commonly in one or two rows below the upper epidermis. They are regularly arranged, elongated cells packed with green chloroplasts. It is in these cells that most of the plant’s photosynthesis occurs. - Spongy mesophyll cells are usually situated between the palisade cells and the lower epidermis. They contain fewer chloroplasts than palisade cells and are irregularly arranged with large spaces between them. This arrangement enables gases and water vapour to move easily between the cells and stomata. Gas exchange There are 3 requirements for efﬁcient gas exchange: - Large surface area - Moist gas exchange membrane: gas must dissolve in water before diffusing - Close contact between the gas exchange membrane and the blood supply: diffusion is only efﬁcient over a short range - greater concentration of required gas on one side of the membrane In mammals, gases are exchanged in the lungs (Figure 2.68). These surfaces are protected from desiccation by being inside the body’s waterproof covering. The surface area of contact between the blood and air is increased by the convolution of the lungs into lobes, by the branching of the bronchioles into smaller and smaller tubules, and by the division of the tubules into clusters of tiny air sacs called alveoli. Gas exchange occurs across the thin walls of the alveoli. Alveoli are: - are the tiny air sacs in our lungs. - There are millions in each lung and they have moist, thin walls. - they massively increase the surface area inside our lungs. - they have a lot of tiny blood vessels called capillaries Mammals - The nasal cavity is a large, air-ﬁlled space behind the nose responsible for warming, moisturizing and ﬁltering the air using hair and mucus. The pharynx is a passageway leading from the nasal cavity to the esophagus and larynx. - Epiglottis is a ﬂap above the trachea that prevents the food from entering the windpipe. - Larynx (voice box) is involved in breathing, producing sound and protecting the tracheae from food aspiration. Trachea is a tubular structure responsible for transporting air. - The Trachea splits into two structures called bronchi leading into each lung. Bronchi then branch off into bronchioles that deliver air to tiny sacs called alveoli. - Alveoli are the gas exchange surface. The alveoli walls consist of ﬂattened cells that are only one cell thick. Capillaries are blood vessels that surround the alveoli sacs so O 2 can enter and CO2 can leave. When oxygen binds with a red blood cell it is called oxyhemoglobin. - The diaphragm is a muscle below the lungs that contracts and expands causing the lungs to inhale and exhale. Fish - Fish have a much more efﬁcient respiratory system than humans since they need to extract maximum amount of oxygen from water and diffusion is slower in liquids than air. - The gills are the respiratory organ for ﬁsh. The gills are protected by an operculum or gill cover. Fish keep a constant ﬂow of water moving across the gill ﬁlaments for efﬁcient gas exchange. - The ﬂow of the capillaries is in the opposite direction to the ﬂow of water to create a concentration gradient. It is called a counter current and causes 95% of oxygen to be obtained from the water passing over the gills. Insects - Insect’s respiratory system is called a tracheal system and consists of holes called spiracles that form a row along both sides of their body. The spiracles are connected to tubes called tracheae - Tracheae lead into smaller tubes called tracheoles which reach to the surface of most cells of the body where gas is exchanged. Types of digestion Chemical digestion - Involves the action of specialised proteins called enzymes - Enzymes break down complex chemical compounds into simpler smaller molecules so they can be absorbed into the blood Physical digestion - Cutting and mashing of the food that occurs by chewing food in the mouth - Break the food down into smaller parts to increase the SA:V ratio so it can be attacked by enzymes. Digestive system - Animal cells are heterophic meaning they obtained their food from an external environment and the digestive system breaks it down and obtains the nutrients. - There are three kinds of digestive enzymes: - amylases , which act on carbohydrates - Proteases, which act on protein - Lipases, which act on lipids Human Digestive System Mouth Mechanical digestion where chewing by teeth to break food into smaller pieces so increases surface area. Chemical digestion which introduces the enzyme via salivary amylase. Epiglottis covers the trachea and tongue creates a bowl. Oesophagus The tube between the mouth and stomach and it pushes the food along to the stomach. Stomach In the stomach, chemical digestion of food, particularly proteins begin. Mechanical digestion also occurs through the churning of food. The length of time food spends in the stomach of the mammal is related to the diet. Carnivores have a simpler stomach when compared to herbivores. Small intestine Much of the process of chemical digestion occurs in the small intestines which is made up of duodenum, jejunum and ileum. The main function of the small intestine is absorption of nutrients and minerals from food. The inside of the small intestine is constructed of folds called villi (singular villus) (Figure 2.58a). The epithelial cells on the surface of the villi have small ﬁnger-like projections called microvilli (Figure 2.58b). These folds and projections provide a large surface area, enabling material in the small intestine to be absorbed quickly. Small molecules diffuse or are actively transported through the walls of the villi into the capillary or lymph vessels to be distributed through the body. Liver Digested food, once absorbed into the bloodstream, travels to the liver, which is the centre of food metabolism. It plays an important role in keeping sugars, glycogen and protein levels in balance in the body. It also detoxiﬁes the blood. Large Intestine Water and salts are absorbed in the large intestine. Materials that remain undigested and unabsorbed, together with bacteria, cellular material from the walls of the intestines, and some water and salts, are eliminated from the digestive system as faeces. Caecum The main functions of the cecum are to absorb ﬂuids and salts that remain after completion of intestinal digestion and absorption and to mix its contents with a lubricating substance, mucus. The internal wall of the cecum is composed of a thick mucous membrane, through which water and salts are absorbed. Guts - Plant matter is more difﬁcult to digest than animal tissues. Plant cells have tough cellulose cell walls that must be broken down before the cell contents can be released. Animals are not able to do this unaided. - Herbivores use microorganisms that live symbiotically in their digestive systems to help them. The breakdown of cellulose occurs during a fermentation process in a specialised part in the digestive tract. These structures are found in either the fore-gut or the hind-gut of different parts of the digestive system (see Figure 2.60) 2.3 Transport Introduction to transport system Effective transport systems in multicellular plants and animals all possess - A system of vessels in which substances are transported - A suitable transport medium - A driving mechanism to ensure substances move in the correct direction Differences are in type of structure present, substances transported and the driving mechanism - Simple plants such as certain algae and moss → no specialised transport tissues and the movement of substances relies on diffusion and active transport through all cells. - Advanced plants such as ferns, conifers and ﬂowering plants → special tissues have developed for transport. - These transport tissues are the vascular tissues and there are two types— xylem and phloem. The Distribution of Vascular Tissue in Flowering Plants - In roots, xylem is found in the centre of roots, usually in a star or cross shape with phloem tissue between the arms of the xylem - In the stem, the xylem and phloem tissue divides into vascular bundles - Bundles of vessels of xylem and phloem continue from the stem up leaf stalks, forming the veins in leaves. Xylem - Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. - Xylem tissue consists of two main types of elements—xylem tracheids and xylem vessels, with other cells such as parenchyma and ﬁbres in between. Movement upwards from root and across - The walls of xylem vessels and tracheids are reinforced with lignin thickenings laid down in rings, spirals or other regular patterns. These thickenings prevent the vessels from collapsing, and help the easy movement of water and dissolved substances. - Fibres give support to the xylem tissue and the parenchyma tissue conducts materials from one region of xylem to another and may function in storage. - The function of xylem is to transport water and dissolved inorganic nutrients, from the roots up the plant to the leaves and the reproductive structures such as ﬂowers. - The movement of water up the xylem vessels occurs mainly as a result of a transpiration stream that develops: as water evaporates through the stomata of leaves, it sets up a concentration gradient across the leaf, creating a suction pull on the water and dissolved minerals in the xylem tissue. Phloem - The phloem is a specialized tissue that transports products of photosynthesis from the leaves to the rest of the plant. There are two types of phloem cells: sieve tube cells and companion cells. - Sieve Tubes: Sieve tube cells are long, thin cells that have large pores and perforated cell walls called sieve plates. They do contain mitochondria and ER but no other organelle. Sieve tube cells are connected end to end and share cytoplasm to form a channel so sugar and other products can ﬂow. - Companion Cells: Companion cells are found alongside sieve tubes and contain a nucleus and other organelles that the sieve tube lacks. They assist the effectiveness of sieve tubes as they provide ATP and nutrients and assist the loading and unloading of sugars into the sieve tube. Xylem Phloem Structure Xylem vessels Phloem ﬁbres Lignin (spirals) Sieve cells + companion cells Substance Water Sugars (glucose), minerals, other nutrients Transport Unidirectional: roots to leaves Bi-directional: wherever sugars are direction required Transport theory Passive transport Translocation: Active transport Pressure-Flow Theory: 1. Root pressure: transverse osmotic pressure within the cells of a root 1. Nutrients moved into phloem system that causes sap to rise by active transport from through a plant stem to the ‘source’ (leaves) leaves 2. Water ﬂows by osmosis, 2. Capillarity: movement caused by creating pressure gradient the attraction of molecules of the 3. Nutrients move passively liquid to the molecules of the solid down phloem, following 3. Cohesion: water molecules bond pressure gradient to each other 4. Sugar actively transported out 4. Adhesion: water molecules bind to of phloem at ‘sink’ walls of xylem tubes 5. Transpiration: evaporation from leaves pulls water through xylem Stomates - Stomata are tiny openings or pores that enable gaseous exchange. Stomata are usually found in plant leaves, but they can also be found in some stems. Stomata regulate gas exchange between the plant and environment and control of water loss by changing the size of the stomatal pore. Lenticels - A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of dicotyledonous ﬂowering plants. It functions as a pore, providing a pathway for the direct exchange of gases between the internal tissues and atmosphere through the bark, which is otherwise impermeable to gases. Cuticles - Plant cuticle is the outermost layer of plants, which covers leaves, fruits, ﬂowers, and non-woody stems of higher plants. It protects plants against drought, extreme temperatures, UV radiation, chemical attack, mechanical injuries, and pathogen/pest infection. Open and closed System A circulatory system is classiﬁed as closed or open, depending on the ﬂoor of its transport ﬂuid. In a closed system the transport ﬂuid ﬂows in vessels only but in an open system, at some stages of circulation the transport ﬂuid leaves the vessels and enters spaces of cavities in the body, bathing the organs directly. In both an open and closed circulatory system, the blood vessels are responsible for the transport of blood and its contents, but the capillary networks (closed system) or ﬂuid in the body cavity (open system) carry out the other functions such as the exchange of nutrients and wastes, and maintaining a stable internal environment in the body of the organism. Open system: - Open circulatory systems are systems where blood, rather than being sealed tight in arteries and veins, suffuses the body and may be directly open to the environment at places such as the digestive tract. - Open circulatory systems use hemolymph instead of blood. This “hemolymph” performs the functions of blood, lymph, and intestinal ﬂuid – which are three different, highly specialized ﬂuids in animals with closed circulatory systems. - Instead of a complex and closed system of veins and arteries, organisms with open circulatory systems have a “hemocoel.” This is a central body cavity found inside most invertebrate animals where both digestive and circulatory functions are performed. This hemocoel may have “arteries” through which the blood can reach tissues – but these arteries are not closed and do not circulate blood as quickly as closed, muscle-assisted arteries. - Arthropods (invertebrates with exoskeletons, such as insects) have open circulatory systems. Closed System - A closed circulatory system is characteristic of all vertebrates such as ﬁsh, frogs, reptiles, birds and mammals (including humans). - The transport ﬂuid is blood which is contained in vessels at all times and never ﬂows through body cavities. - The heart is a muscular organ that pumps the blood around the body. In mammals, the heart may be two-chambered (e.g. ﬁsh), three-chambered (e.g. frogs and some reptiles), or four-chambered as in other reptiles, all birds and mammals. - Blood ﬂows through three types of blood vessels: - veins which carry blood from body organs towards the heart - arteries which carry blood away from the heart to the organs - capillaries which form a link between arteries and veins. - The arteries branch into smaller arterioles which subdivide further into a network of capillaries. These capillaries branch extensively throughout the tissues, so that no cell is very far from a capillary. The exchange of nutrients, wastes and gases takes place between blood in the capillaries and ﬂuid surrounding the cells which the capillaries supply. - Blood remains in the capillaries at all times, but any chemical substances required by cells leave the capillaries in a dissolved form—the ﬂuid containing the nutrients, gases and wastes is called tissue ﬂuid or interstitial ﬂuid. (The tissue ﬂuid makes internal organs appear ‘wet’.). - Capillaries join up to form venules, which in turn join up to form veins, returning blood to the heart. - In a closed circulatory system, the muscular heart pumps blood under high pressure, ensuring efﬁcient transport, which suits large, active animals such as vertebrates. - A four chambered heart is the most efﬁcient pumping mechanism, as it keeps oxygenated and deoxygenated blood separate. (Not all vertebrates have a four-chambered heart—ﬁsh have a heart with only two chambers. Blood Vessels There are 3 types of blood vessels which include arteries, vein and capillaries. All are long and hollow structures. - Arteries carry oxygenated blood to the body from the heart and are under high pressure. Walls of the arteries are thicker to withstand this pressure. The walls are also elastic so it can expand when a pulse of blood moves through. This contraction also propels blood forward. The arteries later branch into smaller arterioles. - Veins carry deoxygenated blood to the heart from the body and are under low pressure. Walls of the veins are thinner and not elastic and the lumen is wider for easy ﬂow. When muscles in tissues contract, walls of the vein are compressed propelling the blood. Veins have valves preventing blood from ﬂowing backwards. Valves open to allow blood to ﬂow through forward but the pressure of trying to ﬂow backwards causes them to shut. - Capillaries are tiny vessels that bring blood into close contact with tissues where the exchange of chemical substances. Wall consists of only one layer for efﬁcient diffusion. Diffusion is a slow process so the structure of capillaries is suited to slowing down the ﬂow of blood and increasing their exposed surface area. Blood remains in the capillaries, but any chemical substances required by cells leave the capillaries in a dissolved form and move to the ﬂuid that surrounds the cells. This ﬂuid is called the interstitial ﬂuid or tissue ﬂuid. Capillaries join up to form venules. Lymphatic System The lymphatic system is a network of tissues and organs that help rid the body of toxins, waste and other unwanted materials. The primary function of the lymphatic system is to transport lymph, a ﬂuid containing infection-ﬁghting white blood cells, throughout the body. 1Blood Main transport medium of the body. Is a transport medium, carries nutrients needed by the body, wastes to be excreted, gases and other chemicals. - Red Blood Cells - Red blood cells (erythrocytes) transport oxygen and form in the bone marrow from adult stem cells. As the cell matures the nucleus disintegrates so more red pigment called hemoglobin can ﬁt. Red blood cells are round, biconcave and ﬂattened towards the center. This shape makes them more pliable so they can ﬁt through capillaries. They have a diameter of 7 micrometers and a lifespan of 4 months. There are approximately 46 million red blood cells per mL of blood. - Red blood cells contain a protein called haemoglobin, which carries oxygen from the lungs to all parts of the body. - White Blood Cells (Leukocytes) - White blood cells (leucocytes) play an important role in the defense of the body and are produced in the bone marrow. They are found in tissue and blood and can pass through capillaries. There are several types of white blood cells with each a speciﬁc function. White blood cells are 50 % bigger than red blood cells. They have a nucleus and there are approximately 400011000 white blood cells per mL of blood. - are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. - Platelets - Platelets (thrombocytes) function in the clotting of blood and are produced in the bone marrow. They are crescent shaped and half the size of red blood cells. There are about 400000 platelets per mL of blood. When there's a wound platelets stick to each other and to the ﬁbers. The contact between ﬁbers and platelets causes them to break open and release an enzyme called thromboplastin which aids in the clotting of blood - Your platelets will clot (clump together) to plug the hole in the blood vessel and stop the bleeding. - Plasma - Plasma is ﬂuid that is 90% water and 10% proteins that makes most of the volume of blood. It carries substances dissolved or suspended from. Besides blood cells it also carries: - plasma protein: clotting factors, immunoglobulin, albumen and enzymes - nutrients: amino acids, glucose, glycerol, fatty acids and cholesterol - gases: oxygen and carbon dioxide - excretory waste products: area, uric acid and ammonia - ions: sodium chloride, calcium and magnesium phosphate - regulatory substances: hormones - other substances: vitamins - Plasma carries water, salts and enzymes. The main role of plasma is to take nutrients, hormones, and proteins to the parts of the body that need it. The Heart The heart pumps the blood around the body. In mammals, the heart has 4 chambers. Top 2 chambers are called atria and bottom 2 are called ventricles. Valves are present between chambers to maintain one directional ﬂow. Deoxygenated blood returns to the right atrium via the superior vena cava and inferior vena cava. It then moves to the right ventricle where it is pumped via the pulmonary artery to the lungs. After the oxygenated blood returns from the lungs to the left atrium via the pulmonary vein it moves to the left ventricle where it is pumped via the aorta to all areas of the body. The left ventricle has the thickest wall since it has to pump the blood to the rest of the body. The circulation of blood in the rest of the body is called systemic circulation while the circulation of blood between the heart and lungs is called pulmonary circulation. Composition Of Blood The composition of blood changes as it moves around the body and depends on the organ it is moving through. In all organs and tissues except the lungs, blood loses oxygen and gains carbon dioxide. In the lungs, it gains oxygen and loses carbon dioxide. In all organs except the small intestine, blood loses nutrients, such as the products of digestion, and gains wastes. Blood gains are products of digestion in the small intestine. In the kidneys, blood has less urea when it leaves, and the concentration of water and salts will have changed according to the needs of the body. 3.1 Ecosystem Dynamics - Population Dynamics Ecosystems - An ecosystem is a combination of all the organisms; a community of living and nonliving things that work together – it consists of abiotic (soil, water, air) and biotic parts (ﬂora, fauna). - Abiotic and biotic factors act on the characteristics of the organisms and affect the ability of an organism to survive and reproduce in a particular environment. Meaning species will have a range of favourable characteristics to survive their environment, if changes happen to the environment the animals might not be able to survive or adapt. - There should be a balance between abiotic and biotic and ecosystems have a signiﬁcant inﬂuence on species diversity. - There are two types of ecosystems - Aquatic: a water environment, 2 main types salt and freshwater and sometimes both. Wetlands, Mangrove swamps, estuaries, rivers, lakes - Terrestrial: found on land. Dessert, grasslands, forest, Woodland - Abiotic factor in aquatic environments are water ﬂow rate, salinity of the water, availability if oxygen, availability of light, temperature range and pressure - Abiotic factors in terrestrial environments are exposure to wind, soil type, temperature, availability to water/light, aspect and topography. - Important biotic factors include abundance of food, variety of disease-causing and number of organism/competitors/mates and predators Selection Pressure in an ecosystem - Selection pressures are all the factors of an ecosystem that inﬂuences changes of survival - Natural selection is a process whereby species which have traits that enable them to adapt in an environment survive and reproduce, and then pass on their genes to the next generation. - Drives natural selection - Those individuals within the population that have random variations that make them better suited to survive in the changed environment are more likely to survive - Genetic based variation are passed from presurvung parents to offspring - Biodiversity is essential for a surviving population → If all organisms were the same, no organisms could adapt to new conditions. - Abiotic pressures: - Temperature - Light intensity - Pressure - Salt concentration Water availability - Biotic Factors - Competition - Prey Availability - Predation In Australia; - Abiotics factors of rainfall, temperature and landform patterns signiﬁcantly affect distribution and abundance of vegetation and ecosystem - Biotic factors affect distribution and abundance organism within these ecosystems Abundance and Distribution - Abundance → How many individuals of that species live throughout an ecosystem - Distribution → Where it is found - Both abiotic and biotic factors affect these Ecology - Ecology is the study of living things and their environment, and all the inter-relationships between the lifeforms and the factors of the environment itself. - Interrelationships determine distribution and abundance of ﬂora and fauna - To understand environmental changes in plant and animal populations over time ecologists collect and record information. - Allows biodiversity within an ecosystem to be assessed - They have two major questions - Why is a species only present in particular places? - What determines the number of individuals (size) of a population in one particular place - In the ﬁelds of ecology they can't always do a heat count to determine the abundances of a species so they use different sampling techniques to make population estimates. Population Trends - Examining population trends can lead to inferences about the species and what abiotic and biotic characteristics they are most suited to. Transects - In large areas transects are commonly used to give an idea of the variation that may occur. - are a narrow strip that crosses the entire area being studied, from one side to the other, drawn to scale - provide an accurate and easy method of representing an area simply. - Two examples are plan sketch and proﬁle sketch - Advantages - Useful when area too large for direction and observation - Useful to determine changes in vegetation with altitude or aspect - Disadvantages - Only record organism found in the transect - May not be an accurate representation of the study site - Plan sketch is an aerial or surface view - it shows the scale distribution of organisms in a measured and plotted view. - Proﬁle sketch is a side-on view of an area showing to scale the distribution of organisms along a line. Measuring Abundance of a species - Attempting to count every single animal in an area is sometimes very difﬁcult, estimating and slow moving counts are much easier - Two methods commonly used are the quadrant method and capture mark recapture. Quadrat Method: - Quadrat sampling is used for plants and slow moving animals - A “quadrat” is a simple wire/wooden/plastic frame which is dropped onto the ground at random throughout the study area. After a number of “drops” (the more, the better) the average number of organisms per quadrant is calculated. cFinally, the estimated population is found by “scaling-up” from the area of the quadrat to the total area being studied. - 120 daisies have been collected in 10 1mx1m quadrats. What is the estimated abundance of daisies in that area → (120/1x10) x 800 - Advantages - More speciﬁc than a transect - This method is beneﬁcial when plant species number are too high in number to count individually - Disadvantages - Only record organisms found in the quadrant - Large numbers of quadrants my be needed to get an accurate representation of entire study area - Only for mobile animals, not for animals that will run, ﬂy or swim. Estimating AN abundance of Animals - First sample, 20 individuals were marked. Second sample 50 were collected, 10 were marked. → (20x50/10) - The technique is based on a number of assumptions for accurate estimates of the total population to be calculated: - There is no population change through migration, births or deaths between the sampling period - All animals are equally able to be caught (individuals are not ‘trap happy’ or ‘trap shy’) - Marked animals are not hampered in their ability to move and mix freely with the rest of the population. - Advantages - Simple method to estimate abundance in mobile populations - Disadvantages - Destructive or damaging to the animals and environment - Expensive, time consuming, labour intensive Changes in Populations over Time - Members in population that survive and reproduce in their habitat carry the traits most suitable for the conditions - Cane Toads - Introduced to Australia in 1935 to control the greyback cane beetle in sugar plantations - Increasing at a fast rate - Speciﬁc structural adaptations and behaviours to suit Australia - Feed at night, no predators, breed all year, absorb water through skin. - The Cane Toads are evolving to be faster, but more prone to arthritis - Predators have increased resistance to the toxin and those reluctant to eat cane toads are ones that survive and reproduce - Red Belly Black snakes have gotten smaller due to the inability to consume the frogs → Snakes big enough to eat them die due to the toxin - The Northern Quoll has developed a Toad aversion mechanism to avoid the consumption of the toads - Prickly Pear - Introduced to Australia to start cochineal dye industry - Due to the lack of environmental pressures prickly pears spread at a rapid rate - Nonetheless, due to the lack of biodiversity, introducing a moth provided a strong selection pressure that quickly reduced the numbers and distribution of the prickly pears. 3.2- Effects of the environment on organisms Adaptations - Organisms are adapted to survive in their natural environment as a result of evolutionary change by natural selection - An adaptation is a characteristic that an organism has inherited and makes it suited for its environment - It is a result of change that arise via mutation, when a cell divides and replicates during the process of reproduction - Structural Adaptation → How an organism is built - Physiological → How an organism functions - Behavioural → How an organism acts and behaves Structural Adaptation- Plants - Desert plants are able to balance photosynthesis and water for cooling purposes without risking dehydration - Xerophytes → Structural adaptations to maximise absorption and storage or water and minimal loss of water - Eucalypts → Waxy leaves to minimise transpiration of water and exposure to sunlight - Cypress Pines → Tiny cylindrical leaves to have a small SA:V ratio Structural Adaptations- Animals - Thorny Devil - Has spikes on its body to make it look more ferocious as well as being harder to swallow by prey - Has scales that absorb water straight into its mouth - Gold and brown camouﬂages in dessert - Wombat - Muscular shoulders and large claws used for extensive digging - Pouch to protect joeys from dirt whilst digging Physiological Adaptations- Plant - Salt tolerant plants are able to maintain metabolic functioning through their cells accumulate sodium and chloride ions - Minimise salt toxicity by increasing water content in vacuole Physiological Adaptations- Animal - Penguins, seals and polar bears convert a lot of their diet to a fat layer to insulate them from the cold - Some animals slow down their metabolic rates so their overall temperature is cooled - Cane toads dig a water tight mucus cocoon for cooling Behavioural Adaptations- Plant - The venus ﬂytrap has adapted to live in nitrogen-poor soils which it obtains via insects - It can act rapidly when it detects an insect - insect becomes trapped and the plant absorbs its nutrients Behavioural Adaptations- Animal - Puffer ﬁsh pumping air into their stomachs and blow up twice their size to frighten predators - Penguins route in packs to reduce time spent in the cold Darwin in the Galapagos Islands - Dariwn observed small ground ﬁnches on the Galapagos Islands - The shape of their beak was observed → Size of beaks differed - Naturally occurring changes in colour, beak size and leg length - Depending on which island they lived on, and the conditions they found themselves in, some birds thrive and reproduced - Charles Noted: - There is a variation in all populations with many variation heritable - There are more organisms born then the environment can sustain - Those individuals that have more suitable characteristics survive - Survivors pass on traits to offspring - Favorable traits will become more numerous if the environment is stable 3.3 - The Theory of Evolution by Natural Selection The theory of evolution by natural selection - Diversity allows adaptations to change in an environment - Species have been developing for billions of years - All theories of evolution share a common basic premises - Living organisms arose from common ancestors or a common life form and have changed over time - Differences that occur among groups of living organisms imply that living things change over time - Similarities occur in living things and suggest a common ancestry; the basic chemistry, inherited from a common life form, has remained relatively unchanged and has been passed down through generations. Biological Diversity - The variety of forms of life on Earth, the diversity of the characteristics of living organisms and the variety of their ecosystems. - Diversity allows for adaptations - Three levels of biodiversity - Genetic → Genetic makeup in a species - Species → Measure of the diversity of species - Ecosystem → Variation of different ecosystems Genetic Diversity - Important for the population to be able to adapt - Environments are constantly changing and pose selection pressures that enable some organisms with favourable characteristics to survive and reproduce - No variation in the population will be more detrimental for an invasive organism or pressure - More genetic diversity = more chance of survival Concept of Natural Selection - Organisms must possess traits that favor their survival in that environment - Variability→ All populations have random differences or variations among members - Heritability→ Variation must be inherited - Over Reproduction→ Organisms produce more offspring than what the ecosystem can sustain - Competition→ The best suited traits will ultimately thrive and reproduce - If there is a sudden change in the environments, those individuals that randomly possess a variation that is an advantage are more likely to survive the changed conditions Diversiﬁcation of Life on Earth - The move form unicellular organisms to multicellular organs began when these cells clustered together - Life began to diversify further with a rise in invertebrates to ﬁsh and amphibians - Followed by the dominance of reptiles - Mammals species then began to dominate - Selection pressures lead to the thrive and extinction of species Microevolution vs Macroevolution - Macroevolution → Takes place over millions of years, usually results in new species - Microevolution→ shorter periods and results in changes of a particular species, but does not create a new species - Small changes can lead to a dramatic difference New varieties or races (Dog Breeds) Convergent Vs Divergent Evolution Convergent - Distantly related species which have moved to similar environments and are exposed to similar selection pressures to evolve similarly Similar habitats, similar variation would be favoured by natural selection to enable them to survive Divergent - Ancestral species radiates into a number of descendant species with both similar and different traits - Usually inﬂuenced by various selection pressures - An example is Darwin's ﬁnches Gradual Natural selection vs Punctuated Equilibrium Gradualism - Populations slowly diverge by accumulating changes in characteristics due to selection pressures - Suggest that transitional forms should exist - Common ancestor - Small variation Punctuated Equilibrium - Occurs in short bursts of rapid change, followed by long period of stability within populations - Mutations are passed on Evolution Of The Platypus - Platypus shows similar features to birds, reptiles and mammals Webbed feet, venom gland, hair on body - Genetic evidence suggest that monotremes split off ﬁrst evolved The ﬁrst split was between marsupials and mammals - Platypus and echidna share common ancestors - Very well adapted to the environment it lives in - Lay an egg with yolk - Platypus can located prey with their eyes closed, by sensing electric pulses given off by muscles - A type of macroevolution 3.4 - The Evidence Evolution - For changes to occur and build up over time requires a dramatic time scale. Evolution of a species depends on the length of generations, change in environmental factors. - Evolution because of early observation of Lamarck, Darwin and Wallace by noticing the similarities between extinct and modern species and similarities between living species. - Evolutionary ideas were all ﬁrst proposed without any knowledge of DNA and genetic inheritance. - As scientiﬁc knowledge has increased, some ideas have been rejected, while some have been supported by new ﬁndings in genetics, developmental biology and palaeontology. - Evolutionary theory is supported by the analysis of similarities between organisms – both living and dead. - These similarities can be in body parts, cell structure, biochemistry, embryo development or even vestigial structures (structures that once performed a function in an ancestor but are now functionless). - The evidence studied to date suggests that the greater the level of similarity, the more closely related two organisms are. Biochemical Evidence - All living things share the same macromolecules such as proteins and DNA and biochemical process such as cellular respiration - Biochemistry is the study of chemicals found in sound - More closely related species have more similar DNA and proteins - Similarities imply they had a common ancestor - Biochemical evidence of evolution is based on the fact that certain enzymes and chemical processes are found in the cells of all or nearly all life on Earth. - Amino Acid Sequencing - Proteins are a component of all living organism - Made up of amino acids - The sequence of amino acids in the protein is analysed and similarities and differences between organisms are identiﬁed. - Differences imply the organism has evolved. - Number of differences is proportional to the length of time since the separated - DNA Hybridisation - Samples of DNA are removed from two different organism - The separated strands of the species to be compared are then mixed. - The two strands combine (reassociation) and form a ‘hybrid’ DNA molecule - The more closely matched the DNA, the tighter the binding. - Heat is applied to determine how tightly the DNA strands have combined. More closely related species have more similar sequences of bases and therefore the strands bind tightly. - DNA Sequencing - The exact order of bases in DNA of one species is compared with a similar fragment of another species. - A piece of DNA is isolated from each organism. - Multiple copies are made, and dye is used to label the bases. - A DNA sequencer is used to graph and print out the sequence of bases, which are then compared. - Organisms that share a common ancestor share fewer differences. - Provides more detailed information than other biochemical methods. - Limitations of biochemical evidence - changes in DNA/amino acid sequences may not be identiﬁed if a particular change that occurred in the past has reverted back to its original form in a more recent organism. - The techniques are complex, expensive and rely on highly specialised micro-computer technology and can only be performed in high technology laboratories. Comparative Anatomy - Study of similarities and differences in the structure of living things - More similarities imply the organism have separated from a common ancestor recently - Homologous Structures (Divergent Evolution) - Differences in structure represent modiﬁcation. - Organisms that have the same basic plan to their structure but show modiﬁcations are called homologous – they have the same evolutionary origins. - Analogous Structures (Convergent Evolution) - Structures that look similar but are very different (e.g. wings of bird and wings of grasshopper) - May have started off differently but over time evolve to look similar. - E.g. Australian Echidna and European Hedgehog - Do not show evolutionary relatedness – shows the evolution of structures for a common purpose. - Vestigial Structures - Evolutionary remnants of body parts that no longer serve a useful function. - Provides evidence of common ancestry. - E.g. presence of coccyx and appendix in humans Comparative Embryology - Comparison of development stages of an organism - Related species show similarities in development - Fish, mammals, amphibians, birds Biogeography - Study of the distribution of organisms - For a new species to arise, it must be genetically isolated. - Some continents share very similar organisms even though they are separated by large stretches of ocean because they were once joined together. - Biogeography is the study of the geographical distribution of organisms, both living and extinct. - For a new species to arise, a group of individuals must become isolated (geographically separated) from the rest. - Predictions based on biogeography provide evidence to support this feature of the theory of evolution. - If isolation is a criterion necessary for a new species to arise from an original species, the new species should resemble species with which they shared a habitat. - They will similar to: - Species that lived close by than species found far away - Species that lived in a common area before it split up Biogeography: Darwin ﬁnches and wallace's Line - Darwin’s famous studies of numerous animals on the Galapagos Islands - Alfred Russell Wallace was a naturalist working at the same time as Darwin and he also heavily contributed to our modern understanding of Evolution and Natural Selection - Wallace found that the fauna (animal species) of Asia and Australia, which are strikingly different, divide along a line that runs through Bali and Borneo, continues north through Lombok and Sulawesi, and then east of the Philippines. Biogeography: Evidence - Flightless birds and continental drift - Present day distribution ﬂightless birds suggests these birds originated from a common ancestor on Gondwana and different populations evolved on isolated southern continents as they drifted apart - Emus in Australia, Ostriches in South Africa, Kiwis in New Zealand, Rheas in South America - Also no similar ﬂightless birds on northern continents as this area became isolated from Gondwana before these birds arose Fossil Evidence - Fossils provide direct evidence of the existence of an organism in the past - The sequence in which fossils are laid down in a rock reﬂects the order in which they were formed - Law of Superposition - Further down in a rock represent an older fossil - Relative dating relies on the assumption that the fossils higher up in the rock are younger than the lower fossils → Fossils are dated relative to one another - Absolute dating enables the actual age of the specimen to be determined by using radioactive elements that are present Microevolution - The inﬂuence of physical and chemical change in the environment on micro- evolution is also signiﬁcant. - It is evident in examples of living organisms that we study today (e.g. the peppered moth, DDT resistance in insects and antibiotic resistance in bacteria) and helps us to understand the concepts of convergent and divergent evolution, and to explain ‘modern’ examples of natural selection. Modern Day Evolution Cane Toad - Faster and larger cane toads have reproduced more, hence the whole population is slowly getting faster - Red-belly black snakes have developed a smaller mouth so they are incapable of consuming the organism - There are no selection pressures on the cane toad, hence they will be able to continue to reproduce at exponential rates. Antibiotic resistant Bacteria - Antibiotics are chemical that inhibit the growth of bacteria or destroy them → Target cell wall and inhibit cell metabolism - When penicillin and other antibiotics were introduced the threat posed by infections was reduced - However, strains of bacteria has developed that are not affected by antibiotics - The bacteria that survives passes on genes which leads to a whole new variation of bacteria 4.1- Population Dynamics - Biosphere: part of earth which contains life - Environments can positively or negatively impact an organism - An organism living and non-living surrounds its ecosystem Ocean - Top layer photice - Main producers are photosynthetic phytoplankton and effect by availability of sunlight which reaches about 200m depp → impact temperature of water - Oxygen decreases to a minimum 1000m but rapidly increases again the deeper you go due to mixing water with deep, cold and high oxygen ocean currents that originate in the polar regions. - Food chains are superﬁcial pelagic communities free swimming and ﬂoating organisms and benthic communities of organisms of the deep ocean Biotic Impact factors - Each organism abundance affects the other abundance, different species interact with one another and the interaction smya be positive, negative or neutral fro species - Food chain can determine the negative or positive effect of the biotic and abiotic system - Living organisms can affect each other by predation and symbiosis but also have an equally profound effect on resources - Food sources, mates, light, nutrients, water - Predator/prey relationship - This a feeding relationship where the predator obtains its food by killing its prey eg spiders eating ﬂies - In ecosystems abundance of a predator and its prey can ﬂuctuate through time, predator numbers may copy those of the prey. - Factors that affect number of predator/prey populations are: - Number of predators competing for the same food - Availability of food for the pray - Birth and death rate affecting number of females and mails - Size of ecosystem - Movement between ecosystem - Competition - Competition is usually for a resource in the environment that is limited supply but valuable for survival - All competition involves risk to the competitors and the rewards must outweigh the inherent risk - Normally results in one winner and loser, short term → the winners population will increase whilst looser population will decrease. Long term → can lead to degradation of the environment, decline in diversity and extinction/evolution. - Intraspeciﬁc → Within a species - Interspeciﬁc → Between species - Animal species - Competition may be for mates, food, shelter or hiding places - Animals also possess various defence mechanisms - Plant species - Allelopathy - Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that inﬂuence the germination, growth, survival, and reproduction of other organisms. - Some trees and shrubs release inhibiting chemicals from their roots. The inhibitors slow down or prevent germination and growth of the seeds and seedlings of other plants. - Symbiosis→ Festival/ beneﬁcial - Interactions in which two organisms live together in a close relationship that is beneﬁcial to at least one of them - Obligate relationship → species depend on each other to live - Mutualism→ Postival/ beneﬁcial - Both organism beneﬁt - Clownﬁsh and sea anemone → Clown ﬁsh is protected by the sea anemone whilst the ﬁsh cleans the plant - A mother koala will regurgitate “pap” from her gut to feed her baby. The pap contains the mutualistic bacteria that the baby must have to digest the tough gum leaves. - Commensalism - One species is beneﬁted whilst the other is not harmed or helped - Advantages for the member that can be food, shelter or transport. - Example is a bird nesting in a tree. The bird family gains the important beneﬁt of a relatively safe and secure nest site, while the tree neither gains nor loses. - Parasitism - Porosity - host parasitism is a relationship in which one organism feed on another without killing it, or even necessarily harming it signiﬁcantly - Parasite obtains shelter from the host organism while feeding upon the tissue and ﬂuids - Other parasites, such as leeches and ticks, are “casual” parasites who attach to a host, take a feed of blood, and then drop off and live independently until hungry again. - More serious are the many micro-organisms which can cause infectious diseases. - These parasites include bacteria, viruses and a few protozoans and fungi. They invade the host’s body, feeding and reproducing so that the host becomes sick and may even die. Niche - Niche is that part of the ecosystem that the organism occupies, no two species can occupy the same nichs: competitive exclusion principle. - Fundamental niche → The perfect conditions and resources for an organism to live and reproduce; no competitors, predators or parasites - Realised Niche → All the aspects of the ecosystem including the interactions of other species; restriction placed on them by other organisms. - Example is a miner bird and galah can occupy the same area but as have different food and nesting strategies they occupy different niches within the same habitat - A variety of niches are possible if there is a diversity of biotic and abiotic factors in an eare Predicting consequences for population in Ecosystem - Predation - Predators affect distribution and abundance of their prey; effect→ size of ecosystem, number of shelter sites, birth/death rate and availability of food for prey - Population control - Natural communities abundance predator and prey ﬂuctuate through time - Competition - Competition between species for resources affect the reproduction and survival rates - Short term effect is a decrease in population numbers of one or both species - Different traits may increase or decrease the chance of survival for animals; losing might have to learn to adapt - Symbiosis - Increased evolutionary diversiﬁcation - Development of new species from the integration of genetic material - More resilient ecosystems → Biodiversity - Disease - Any process that adversely affects the normal functioning of tissue in a living organism - Bacteria, virus, Pathogen - Alter the balance of food webs → Affected species will decline in numbers Recent extinction Changed in climate - The continent dried out due to the ice age and rainforests contracted due to a drying climate - Rainforests were contracting – stored moisture and returned moisture to the atmosphere. - Eucalypt forests replaced these, and water was not as efﬁciently retained. - Became hotter and drier, ﬁres broke out due to lightning. - Plants and animals that survived the drought and ﬁre reproduced, changing the ﬂora and fauna The arrival of Humans - Aborigines arrive in australia about 40 000 - 50 000 years ago - Aborigines were extremely successful predators and they used ﬁre to burn back the bush to regenerate grasses for animals and themselves as increasing the abundance of animals meant that there would be more available for hunting. Made use of natural resources to keep everything balanced - introduction of dingoes may have reduced the diversity of carnivore predators. Level Of Nutrients - Low level of nutrients in the soil → dry - Led to smaller animals →F can be sustained on less - Evidence for this can be seen in the smaller size of mammals in Australia compared to counterparts across the world. 4.2 Past ecosystems Superposition - Superposition is layers of silt or mud on top of each other form sedimentary rock. The resulting rock contains a series of horizontal layers or strata. Each layer contains fossils that are typical for a speciﬁc time period during which they were made. - Law of superposition → oldest layer at bottom and newest at top. - British naturalist William smith studied mines and proposed that rock layers with the same type of fossils must have been laid down at the same time. - Danish anatomist and geologist Nicholas Steno observed landscapes around him and came up with the superposition that older layers of rocks are deeper and younger layers lie on top of them. Aborignal and torres strait islanders histories and cultures - West kimberly rock paintings - Wandjina 50,000 to 60,000 years old - Bradshaw 40,000 years old - Types and number animals in the paintings have changed over time and scientist have interpreted this a s indication a series of climate changes - 40,000 tropical forest - 10,000 decreases in rainfall and cooling period occurrence scrub and open grasslands - Changes in types of animals suggest changes in ecology of an area. Geological Evidence - Allows reconstruction of timeline of events - Represents the course of changes in geological and fossil deposits - Banded iron Formations - Form of geochemical evidence found in Australia - Earth's atmosphere has undergone changes, change from anaerobic to aerobic - Form of iron rich and iron poor sediments - Prokaryotes lead to an increase in oxygen concentration in the ocean, - leading to precipitation of insoluble iron oxide - Precipitate accumulated at the bottom of the ocean, forming an iron rich layer of sediments - Great oxygenation event transformed Earth’s atmosphere - resulted in much larger and multicellular organism→ Organisms had to adapt to more oxygen Palaeontological Evidence: Fossils - Palaeontology is the study of fossils. Fossils are the preserved remains, impressions or traces of organisms found in ice, rocks, amber, coal deposits or soil. These remains are hard structures that are not easily destroyed or are slow to decompose. - MICROFOSSILS ARE the tiny remains of bacteria, protists, fungi, animals, and plants.... For example, fossils of bacteria, foraminifera, diatoms, very small invertebrate shells or skeletons, pollen, and tiny bones and teeth of large vertebrates, among others, can be called microfossils. A usually rounded or columnar sedimentary structure consisting of alternating layers of carbonate or silicate sediment and fossilized microbial mats, produced over geologic time by the trapping, binding, or precipitating of minerals by groups of microorganisms, primarily cyanobacteria. - Soils and paleosols can form because of lengthy episodes of landscape stability, in which case they may eventually mark a stratigraphic di- astem or unconformity; they can also form in terres- trial depositional systems that are aggrading as long as the rate of sedimentation does not overwhelm the rate of pedogenesis. - Fossils offer clues to the selection pressures of living things like the climate and environment at the time. - Found in sedimentary rocks → Preserve evidence rather than destroying it - Fossilised soils contain large concentrations of carbon that indicate presence of life - Chemosynthesis is a process where organisms use inorganic compounds available from their environment. - The fossils formed from stromalites provide valuable informationof early orgaims and the environment in which they lived Ice Core Drilling - Accumulation of ice layers in places such as antarctica leaves an annual record of gas and dust in that atmosphere of that time - Scientists can drill into the ice, extract gases and reconstruct the climate record - Increases understanding of past environments Antarctic snow - forms as layers, deeper layers representing ancient deposition events - Special property that it accumulates information about abiotic and biotic factors present at the - time the ice was formed - As snow falls year after year, gases and particles from the atmosphere are trapped within it (wind blown dust, pollen, volcanic ash, radioactive particles, bubbles of atmospheric gas) - Best places for sampling is where temperature never rises above 0 degrees Celsius eg Greenland, Antarctica and high mountain ranges Dating fossils To establish the age of a rock or a fossil, researchers use some type of clock to determine the date it was formed. Geologists commonly use radiometric dating methods, based on the natural radioactive decay of certain elements such as potassium and carbon, as reliable clocks to date ancient events. Relative dating Relative dating is the process of determining if one rock or geologic event is older or younger than another, without knowing their speciﬁc ages—i.e., how many years ago the object was formed Radiometric Dating - Process where scientists determine the age in years of a fossil, rock or mineral - Based off the content of radioactive isotopes - Unstable isotopes change to form stable isotopes → Undergoes radioactive de

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