Biology 1110 Test 1 PDF

Slide 1 Biology 1110 Test 1 1. Levels of Biological Organization: Biological organization refers to the hierarchical arrangement of living things, from the smallest to the largest components: (a) Biosphere: The entire global sum of ecosystems, the zone of life on Earth, including land, water, and...

Slide 1 Biology 1110 Test 1 1. Levels of Biological Organization: Biological organization refers to the hierarchical arrangement of living things, from the smallest to the largest components: (a) Biosphere: The entire global sum of ecosystems, the zone of life on Earth, including land, water, and the atmosphere. (b) Biome: Large geographic biotic communities characterized by climate, soil, plants, and animals (e.g., tundra, desert, rainforest). (c) Ecosystem: A system consisting of abiotic (non-living) components and biotic (living) components interacting in a specific area. - Abiotic components: Non-living factors like temperature, water, soil, sunlight, and air. - Biotic components: Living organisms such as plants, animals, fungi, and microorganisms. (d) Community: A group of different species that interact with each other in the same area. (e) Population: A group of individuals of the same species living and interacting in a particular area. (f) Species: A group of organisms that can interbreed and produce fertile offspring. (g) Organism: An individual living being that can function independently, such as an animal, plant, or bacterium. (h) Organ: A structure composed of multiple tissues working together to perform a specific function (e.g., heart, liver, leaf). (i) Tissue: A group of similar cells working together to perform a specific function (e.g., muscle tissue, epithelial tissue). (j) Cell: The basic unit of life, consisting of various organelles and structures, capable of carrying out all life functions. (k) Organelle: Specialized structures within a cell, such as the nucleus, mitochondria, and ribosomes, that perform specific tasks. (l) Molecule: Groups of atoms bonded together, like DNA, proteins, and lipids, essential for cellular functions. (m) Atom: The smallest unit of matter, consisting of protons, neutrons, and electrons. 2. Characteristics Shared by All Living Things: All living organisms share several key characteristics, which include: - Organization: Living organisms have a complex structure, organized from molecules to cells to tissues and so on. - Metabolism: The chemical processes that occur within an organism to maintain life, including energy production and consumption. - Homeostasis: The ability to maintain a stable internal environment, such as regulating temperature and pH. - Growth and Development: Organisms grow and develop according to genetic instructions (e.g., from embryo to adult). - Reproduction: The ability to produce offspring, either sexually or asexually. - Response to Stimuli: The ability to respond to changes in the environment (e.g., light, temperature, and food availability). - Adaptation through Evolution: The process by which organisms evolve over generations to better survive in their environments. 3. Abiotic and Biotic Components of Ecosystems: - Abiotic components: Non-living factors that influence ecosystems, such as: - Water: Essential for life and influences climate and weather patterns. - Temperature: Affects metabolic rates and survival of organisms. - Soil: Provides nutrients for plants and affects plant growth. - Sunlight: Drives photosynthesis, which is the primary energy source for ecosystems. - Air: Provides oxygen for respiration and carbon dioxide for photosynthesis. - Biotic components: Living organisms in an ecosystem, such as: - Producers: Plants, algae, and some bacteria that synthesize food through photosynthesis. - Consumers: Herbivores, carnivores, omnivores that consume producers and other consumers. - Decomposers: Fungi, bacteria, and other organisms that break down dead organic matter.  4. Main Components of the Cell Theory: The cell theory is one of the fundamental principles in biology: 1. All living organisms are made of one or more cells. 2. The cell is the basic unit of structure and function in organisms. 3. All cells arise from pre-existing cells. 5. Prokaryotic vs. Eukaryotic Cells: - Prokaryotic cells: Simple cells without a nucleus or membrane-bound organelles (e.g., bacteria, archaea). - DNA is free in the cytoplasm. - Typically smaller in size. - Have a cell wall, plasma membrane, and ribosomes. - Eukaryotic cells: Complex cells with a defined nucleus and membrane-bound organelles (e.g., plants, animals, fungi). - DNA is enclosed in the nucleus. - Larger in size. - Have specialized organelles (e.g., mitochondria, chloroplasts). 6. Multicellular, Unicellular, and Colonial Organisms: - Unicellular organisms: Organisms that consist of a single cell (e.g., bacteria, yeast). - Multicellular organisms: Organisms made up of multiple cells that work together to perform various functions (e.g., humans, trees). - Colonial organisms: A group of genetically identical cells that live together and can perform independent functions but often benefit from cooperative behavior (e.g., Volvox, a type of algae).  7. Structure and Function of Cellular Structures: (a) Cell (Plasma) Membrane: Semi-permeable membrane that surrounds the cell, controls the movement of substances in and out of the cell. (b) Cell Wall: Rigid outer layer found in plants, fungi, and bacteria, providing structure and protection. (c) Cytoplasm: Gel-like substance inside the cell, where most cellular processes occur. (d) Nucleus: Membrane-bound organelle that contains genetic material (DNA). (e) DNA: Genetic material responsible for inheritance and guiding cellular activities. (f) Endoplasmic Reticulum (Rough & Smooth): - Rough ER: Has ribosomes attached, involved in protein synthesis and modification. - Smooth ER: Lacks ribosomes, involved in lipid synthesis and detoxification. (g) Ribosome: Small structures where protein synthesis occurs. (h) Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for transport inside or outside the cell. (i) Lysosome: Contains digestive enzymes to break down waste materials and cellular debris. (j) Central Vacuole: Large, fluid-filled organelle in plant cells, involved in storage, waste disposal, and maintaining cell rigidity. (k) Mitochondria: Powerhouses of the cell, responsible for energy production (ATP) through cellular respiration. (l) Chloroplast: Found in plant cells, responsible for photosynthesis, converting sunlight into chemical energy. 8. Define Cellular Respiration and Photosynthesis: - Cellular Respiration: The process by which cells convert glucose and oxygen into ATP (energy), carbon dioxide, and water. It occurs in the mitochondria. - Photosynthesis: The process by which plants and some bacteria use sunlight to synthesize foods (glucose) from carbon dioxide and water, releasing oxygen as a byproduct. It occurs in the chloroplasts. 9. Compare and Contrast Animal Cells and Plant Cells: - Plant Cells: - Have a cell wall made of cellulose. - Contain chloroplasts for photosynthesis. - Have a large central vacuole for water and waste storage. - Animal Cells: - Lack of a cell wall and chloroplasts. - Have smaller vacuoles, and their shape is more flexible. - Contain centrioles for cell division, which plant cells lack. Both cell types have a nucleus, mitochondria, endoplasmic reticulum, ribosomes, and Golgi apparatus, among other organelles. Slide 2 Biology 1110 Test 1 1. Hypothesis, Theory, Testability, and Falsifiability - Hypothesis: A hypothesis is a testable and falsifiable statement or prediction about the relationship between two or more variables. It is an educated guess based on existing knowledge and observations that can be tested through experimentation or further observation. - Distinguishing Hypothesis from Theory: - Hypothesis: A hypothesis is a specific, testable prediction, often formed as an "if... then..." statement, which can be tested and either supported or refuted. - Theory: A theory is a broad, well-substantiated explanation of some aspect of the natural world that is based on a body of evidence and has stood up to repeated testing. A theory can explain multiple observations and hypotheses. - Testable and Falsifiable: - A hypothesis is testable if it can be evaluated through experimentation or observation to determine its validity. - A hypothesis is falsifiable if there is a possibility of the hypothesis being proven false. For a hypothesis to be scientific, it must be possible to design an experiment or make observations that could potentially contradict it. 2. Steps in the Scientific Method The scientific method is a systematic way of investigating questions and testing ideas: 1. Observation: Begin by observing phenomena or existing data to identify a question or problem. 2. Research: Gather existing information on the topic to understand previous findings and context. 3. Hypothesis: Formulate a testable hypothesis or prediction based on observations and research. 4. Experimentation: Conduct controlled experiments or gather data to test the hypothesis. 5. Analysis: Analyze the results using statistical methods to determine if they support or refute the hypothesis. 6. Conclusion: Draw conclusions based on the data. If the hypothesis is supported, further testing or development of a theory might follow. If refuted, refine the hypothesis or explore alternative explanations. 7. Communication: Share findings with the scientific community for peer review and further research. 3. Components of Experimental Design (a) Independent Variable and Dependent Variable: - Independent Variable: The factor that is manipulated or changed in an experiment to observe its effect. It is the cause in a cause-and-effect relationship. - Dependent Variable: The factor that is measured or observed in response to changes in the independent variable. It is the effect in the cause-and-effect relationship. Example: In an experiment to test the effect of sunlight on plant growth: - Independent Variable: The amount of sunlight the plants receive. - Dependent Variable: The growth of the plants (e.g., measured in height). (b) Null Hypothesis and Alternate Hypothesis: - Null Hypothesis (H₀): The null hypothesis states that there is no effect or no relationship between the variables being studied. It is the hypothesis that is tested statistically, and if it is rejected, the alternate hypothesis is considered. - Alternate Hypothesis (H₁): The alternate hypothesis proposes that there is a significant effect or relationship between the variables. Example: - Null Hypothesis: There is no difference in plant growth between the two groups. - Alternate Hypothesis: The plants exposed to sunlight will grow taller than those not exposed. (c) Controlled Experiment: A controlled experiment is an experiment in which all variables except for the independent variable are kept constant to isolate its effect on the dependent variable. This is done to ensure that observed effects are due to the independent variable alone, not confounding factors. - Treatment Group: The group that receives the experimental treatment or manipulation of the independent variable. - Control Group: The group that does not receive the experimental treatment and is used as a baseline to compare the treatment group against. Example: In an experiment testing a new fertilizer, the control group would receive no fertilizer, while the treatment group would receive the fertilizer. (d) Random Selection and Standardizing External Variables: - Randomly selecting subjects helps reduce bias and ensures that the sample is representative of the population. It helps to ensure that every individual has an equal chance of being chosen. - Standardizing External Variable: To ensure that other variables do not influence the experiment, it's important to control or standardize external factors (e.g., temperature, time of day, or environmental conditions) that could affect the results. (e) Replication and Statistical Analysis: - Replication: Repeating experiments helps ensure that results are reliable and not due to chance. Multiple replications increase the robustness of the findings. - Statistical Analysis tests are used to determine if the results are significant (i.e., unlikely to have occurred by chance) and to analyze relationships between variables. 4. Definitions of Evolution, Natural Selection, and Adaptation - Evolution: Evolution refers to the process by which populations of organisms change over generations through variations in traits, inheritance, and selection pressures. - Example: Over millions of years, the beaks of finches on the Galápagos Islands evolved to adapt to different food sources available on different islands. - Natural Selection: Natural selection is the process by which organisms with traits better suited to their environment are more likely to survive and reproduce, passing those advantageous traits to the next generation. - Example: Giraffes with longer necks can reach more food in tall trees, giving them a survival advantage over giraffes with shorter necks. - Adaptation: An adaptation is a heritable trait or behavior that increases an organism's chances of survival and reproduction in a specific environment. - Example: Camouflage in the peppered moth allows it to blend into the environment and avoid predators, which is an adaptation to its environment. 5. Main Steps in Natural Selection Natural selection operates through the following steps: 1. Variation: Individuals within a population vary in their traits (e.g., size, color, shape). 2. Inheritance: Some of these variations are heritable and passed on to offspring. 3. Differential Survival and Reproduction: In a given environment, individuals with advantageous traits are more likely to survive and reproduce than those with less advantageous traits. 4. Change in Population: Over generations, the advantageous traits become more common in the population as those individuals are more likely to reproduce and pass on these traits. 6. Three Conditions for Natural Selection to Cause Evolutionary Change: 1. Variation: There must be variation in traits within a population. Without variation, natural selection cannot act. - Example: In a population of beetles, some may be green, and others may be brown. 2. Heritability: The trait must be heritable, meaning it can be passed down from parents to offspring. - Example: The color of the beatles (green or brown) is determined by genes, which are passed down to offspring. 3. Differential Reproductive Success: Individuals with advantageous traits must have a better chance of surviving and reproducing, passing those traits to the next generation. - Example: In a population of beetles, brown beetles may be less visible to predators, so they are more likely to survive and reproduce than green beetles. As a result, the population becomes predominantly brown over time. Summary - Hypotheses are testable and falsifiable predictions, while theories are broad, well-supported explanations. - The scientific method involves observing, hypothesizing, experimenting, analyzing, and concluding. - Experimental design includes manipulating independent variables, setting up control groups, and ensuring random selection and replication. - Evolution, natural selection, and adaptation describe the processes that drive changes in organisms and populations over time. Slide 3 Biology 1100 Test 1 Definition of Taxonomy and Uses of Classification Systems: ​ Taxonomy is the science of classifying organisms into hierarchical categories based on shared characteristics, such as evolutionary relationships, morphology, or behavior. ​ Practical uses of classification systems include: ○​ Organizing biodiversity for study and conservation. ○​ Helping in identifying and naming organisms. ○​ Aiding in understanding evolutionary relationships. ○​ Guiding medical, agricultural, and ecological practices. ○​ Assisting in preserving and protecting endangered species. Carolus Linnaeus’s Taxonomic System: ​ Taxonomic Hierarchy: ○​ Linnaeus developed a hierarchical classification system, which arranges organisms into a series of nested levels. The main levels are: 1.​ Domain 2.​ Kingdom 3.​ Phylum 4.​ Class 5.​ Order 6.​ Family 7.​ Genus 8.​ Species ​ Binomial System of Nomenclature: ○​ This system assigns every species a two-part Latin name: the genus (capitalized) and the species (lowercase). Example: Homo sapiens (human). ○​ This system standardizes naming and allows consistent identification. Biological Species: ​ A biological species is defined as a group of organisms that can interbreed and produce fertile offspring under natural conditions. They are reproductively isolated from other such groups. Phylogeny and Systematics: ​ Phylogeny refers to the evolutionary history and relationships among species or groups of organisms, often depicted as a phylogenetic tree. ​ Systematics is the scientific study of the diversity of organisms and their evolutionary relationships, combining taxonomy and phylogeny. Darwin’s Influence on Biological Classification: ​ Charles Darwin’s theory of evolution by natural selection significantly influenced biological classification. Darwin proposed that species evolve over time and that  similarities between species reflect common ancestry. Thus, taxonomy is now more closely tied to phylogeny (evolutionary history) rather than just morphological characteristics. Phylogenetic Tree: ​ A phylogenetic tree is a branching diagram that represents the evolutionary relationships among different species or groups. It shows how species are related to each other, with common ancestors at branching points. ​ The tree helps interpret the evolutionary history, common traits, and divergence of species over time. Natural vs. Artificial Classification Systems: ​ Natural classification systems are based on evolutionary relationships and are informed by phylogenies. They reflect common ancestry. ​ Artificial classification systems group organisms based on observable characteristics, regardless of evolutionary relationships. These may not always reflect evolutionary history accurately. Clade: ​ A clade is a group of organisms that consists of a common ancestor and all its descendants. It represents a single branch of the evolutionary tree. Limitations of the Current Biological Classification System: ​ The current system does not fully achieve a "natural" classification because some organisms may share similar characteristics due to convergent evolution (unrelated species evolving similar traits due to similar environments). Furthermore, the classification system is based on available genetic and morphological data, which may not capture all evolutionary relationships. Three-Domain System of Classification: ​ The three-domain system, proposed by Carl Woese, classifies life into three main domains: 1.​ Archaea: Single-celled organisms that are distinct from bacteria and live in extreme environments. 2.​ Bacteria: Single-celled organisms with simple cell structures, typically found in a wide range of environments. 3.​ Eukarya: Organisms with complex, membrane-bound cells, including animals, plants, fungi, and protists. Chronological Sequence of Major Events in Evolutionary History (based on Table 25.1 in your textbook): ​ The major events in the evolution of life on Earth, in chronological order, include: 1.​ Formation of Earth (~4.5 billion years ago) 2.​ First prokaryotic cells (around 3.5 billion years ago) 3.​ Photosynthesis and oxygen production by cyanobacteria (~2.7 billion years ago) 4.​ Eukaryotic cells appear (~2.1 billion years ago) 5.​ Multicellular life emerges (~1.2 billion years ago) 6.​ First animals appear (~600 million years ago) 7.​ Cambrian Explosion (~540 million years ago) 8.​ Colonization of land by plants (~475 million years ago) 9.​ Vertebrates invade land (~360 million years ago) 10.​Dinosaurs dominate (~230 million years ago) 11.​Mass extinctions, including the Cretaceous-Paleogene extinction (~65 million years ago) 12.​Emergence of mammals and birds (~65 million years ago) 13.​Evolution of humans (~2.5 million years ago) Slide 4 Biology 1100 Test 1 1. Environmental (Abiotic) Conditions for All Living Systems Living systems require specific abiotic conditions to maintain homeostasis and support life processes. These include: ​ Temperature: Living organisms have specific temperature ranges for enzymes to function optimally. Too high or too low temperatures can inhibit biochemical reactions or damage cellular structures. ​ Water: Water is necessary for biochemical reactions, including metabolism, and provides a medium for cellular processes. It also helps maintain cellular structure through turgor pressure. ​ Oxygen: For aerobic organisms, oxygen is required for cellular respiration, the process by which cells generate energy. ​ pH: The pH of the environment affects enzyme activity and the stability of cellular components. Most organisms are adapted to a narrow pH range. ​ Light: For photosynthetic organisms, light is a primary energy source. ​ Nutrients (Minerals, Carbon, Nitrogen): These are essential for growth and maintenance. Carbon is needed for organic molecule synthesis, and nitrogen is critical for protein and nucleic acid production. 2. Four Major Nutritional Modes in Living Things ​ Autotrophs: Organisms that produce their own food from inorganic materials. ○​ Energy source: Light (photosynthesis) or inorganic chemicals (chemosynthesis). ○​ Carbon source: Carbon dioxide (CO₂). ○​ Example: Plants, algae, cyanobacteria. ​ Heterotrophs: Organisms that rely on consuming organic matter for energy. ○​ Energy source: Organic molecules from other organisms. ○​ Carbon source: Organic molecules. ○​ Example: Animals, fungi, most bacteria. ​ Photoautotrophs: Organisms that use light as an energy source to synthesize organic compounds from CO₂. ○​ Example: Plants, algae. ​ Chemoautotrophs: Organisms that obtain energy by oxidizing inorganic substances (e.g., hydrogen sulfide or ammonia) and use CO₂ as a carbon source. ○​ Example: Certain bacteria in deep-sea hydrothermal vents. 3. Success of Prokaryotes: Distribution and Abundance Prokaryotes are among the most abundant and diverse organisms on Earth due to their:  ​ Adaptability: They can thrive in extreme environments (e.g., extreme heat, acidity, salinity), which allows them to occupy a wide range of ecological niches. ​ Reproduction: Prokaryotes reproduce rapidly through binary fission, leading to exponential population growth. ​ Genetic diversity: Horizontal gene transfer allows rapid adaptation to new environments. ​ Small size and efficiency: Their small size allows them to occupy a variety of habitats and outcompete other organisms for resources. 4. Comparison of Domain Bacteria and Archaea ​ Bacteria: ○​ Have peptidoglycan in their cell walls. ○​ Can be found in a wide range of environments, but typically do not survive extreme conditions. ○​ Can be pathogenic or beneficial. ​ Archaea: ○​ Lack peptidoglycan in their cell walls, and their membrane lipids differ chemically from those in bacteria and eukaryotes. ○​ Often found in extreme environments (e.g., high temperatures, salinity, or acidic conditions). ○​ Genetically more similar to eukaryotes than to bacteria. 5. Roles of Prokaryotes in the Biosphere ​ Ecological Roles: ○​ Decomposers: Break down dead organisms and recycle nutrients in ecosystems. ○​ Pathogens: Some bacteria cause diseases in plants, animals, and humans (e.g., Escherichia coli, Streptococcus). ○​ Mutualistic bacteria: In the human gut, prokaryotes aid in digestion, synthesize vitamins, and protect against harmful microbes. ​ Biotechnology: ○​ Food production: Used in the fermentation of dairy products (yogurt, cheese) and alcoholic beverages. ○​ Bioremediation: Prokaryotes break down pollutants in the environment, such as oil spills. 6. Endosymbiotic Theory for Eukaryotic Evolution The endosymbiotic theory suggests that eukaryotic cells originated from a symbiotic relationship between an early eukaryote and a prokaryote. It proposes that mitochondria and chloroplasts (in plants) are the result of prokaryotes (ancient bacteria) being engulfed by an ancestral eukaryotic cell. These engulfed bacteria provided the host cell with advantages, such as the ability to perform aerobic respiration (mitochondria) or photosynthesis (chloroplasts). 7. Characteristics of Protists and Reclassification Protists share some characteristics: ​ They are eukaryotic, single-celled or multicellular, and lack complex structures such as tissues found in plants, animals, and fungi. ​ They live in moist environments and can be autotrophic, heterotrophic, or mixotrophic. Biologists have split the kingdom Protista into several new kingdoms (e.g., Excavata, Chromalveolata) because protists are highly diverse and do not represent a single evolutionary lineage. 8. Key Characteristics and Ecological Roles of Protists ​ Animal-like Protists (Protozoa): ○​ Heterotrophic and usually motile. ○​ Example: Amoeba, Paramecium. ○​ Ecological role: Predators of bacteria and other protists. ​ Plant-like Protists (Algae): ○​ Autotrophic and contain chlorophyll for photosynthesis. ○​ Example: Euglena, diatoms. ○​ Ecological role: Primary producers in aquatic ecosystems. ​ Fungus-like Protists: ○​ Absorb nutrients through external digestion. ○​ Example: Slime molds. ○​ Ecological role: Decomposers. 9. Distinguishing Characteristics of Fungi ​ Fungi are eukaryotic, non-photosynthetic organisms that absorb nutrients through external digestion. ​ They have cell walls made of chitin, unlike plants, which have cellulose. ​ They can be unicellular (yeasts) or multicellular (molds, mushrooms). ​ They reproduce both sexually and asexually through spores. 10. Roles of Fungi ​ Ecological Roles: ○​ Decomposers: Fungi break down dead organic matter, recycling nutrients. ○​ Mutualism: Mycorrhizal fungi form symbiotic relationships with plant roots, aiding in nutrient absorption. ○​ Pathogens: Some fungi cause diseases in plants (e.g., wheat rust) and animals (e.g., Athlete's foot). ​ Biotechnology: ○​ Food production: Used in the production of bread, beer, and cheese. ○​ Antibiotics: The discovery of penicillin from the mold Penicillium revolutionized medicine. Slide 5 Biology 1100 Test 1 1. Definition of Plants and Distinction from Multicellular Protists ​ Plants: Multicellular, eukaryotic organisms that are autotrophic (photosynthetic), with cell walls made of cellulose. They typically have specialized organs (roots, stems, leaves) and are primarily adapted for life on land. ​ Distinction from Multicellular Protists: While multicellular protists (e.g., brown algae) are also eukaryotic, they lack true plant organs (roots, stems, leaves), and their cell walls are made of different materials (e.g., algin in algae). Protists can also live in aquatic environments, whereas plants are adapted for terrestrial life. 2. Basic Resources Required by Plants Plants require the following basic resources: ​ Water: Essential for photosynthesis and the transport of nutrients and sugars through the plant. It also helps maintain turgor pressure in plant cells. ​ Carbon Dioxide (CO₂): Used in photosynthesis to produce glucose and oxygen. ​ Mineral Nutrients: These are absorbed through the roots, including nitrogen (for amino acids and proteins), phosphorus (for energy transfer and DNA/RNA), potassium (for enzyme activation), and other trace elements. ​ Sunlight: Provides the energy for photosynthesis, the process by which plants convert light energy into chemical energy. ​ Oxygen (O₂): Needed for respiration, which occurs in plant cells to release energy stored in glucose. 3. Comparison of Water and Land as Habitats for Plants (a) Availability of O₂, CO₂, Mineral Nutrients, and Light ​ Water: ○​ High availability of water and minerals from the environment. ○​ CO₂ is absorbed through water but may be limited in aquatic environments. ○​ Oxygen is often limited in water (except near the surface). ○​ Light is limited to shallow waters due to absorption by water and sediments. ​ Land: ○​ Oxygen and CO₂ are abundant in the air. ○​ Mineral nutrients are available in the soil but need to be absorbed by plant roots. ○​ Light is more abundant on land, but the plant needs adaptations to avoid desiccation (drying out). (b) Support ​ Water: Water provides buoyancy, so plants do not need complex structural support.  ​ Land: Plants require structural adaptations, such as lignin in cell walls, to prevent wilting and support the plant’s upright growth. (c) Reproduction and Dispersal ​ Water: Water facilitates the movement of gametes, so reproduction can occur easily in water. Dispersal of offspring is typically by water currents. ​ Land: Land plants require adaptations for gamete dispersal (e.g., pollen in seed plants) and often rely on wind, animals, or water for dispersal of seeds or spores. 4. Evolutionary History of Plants ​ (a) Origin from Plant-like Protist Ancestors: Plants evolved from green algae, specifically a group called charophytes, which share key features with land plants, such as chlorophyll a and b and cellulose in cell walls. ​ (b) Expansion onto Land: Plants moved onto land around 500 million years ago. This required adaptations to conserve water, support themselves against gravity, and reproduce in a dry environment. ​ (c) Vascular Tissue: The evolution of vascular tissue (xylem and phloem) allowed plants to efficiently transport water, nutrients, and sugars throughout their bodies, facilitating the colonization of land. ​ (d) Seeds: The evolution of seeds allowed plants to reproduce without water. Seeds are adapted for dormancy, enabling plants to survive unfavorable conditions and disperse over greater distances. ​ (e) Flowers and Fruit: Flowers and fruits evolved in angiosperms (flowering plants) to attract pollinators and disperse seeds effectively, which enhanced reproductive success. 5. Vascular vs Non-Vascular Plants ​ Vascular Plants: Have specialized vascular tissues (xylem and phloem) for transporting water, nutrients, and sugars. Examples: ferns, gymnosperms, angiosperms. ​ Non-Vascular Plants: Lack vascular tissues. They rely on diffusion for transport and tend to be small and grow in moist environments. Examples: mosses, liverworts. 6. Key Adaptations to Life on Land ​ (a) Mosses: ○​ Adaptations: Small size, water-conducting cells (but not vascular tissue), and a dominant gametophyte stage. ○​ Advantage: Mosses can survive in damp environments, where they absorb water and nutrients directly through their surfaces. ​ (b) Seedless Vascular Plants: ○​ Adaptations: Vascular tissue (xylem and phloem), true leaves, and roots. ○​ Advantage: Ability to transport water and nutrients efficiently, allowing them to grow larger and colonize diverse terrestrial environments. ​ (c) Gymnosperms:  ○​ Adaptations: Seeds, which allow reproduction without water, and needle-like leaves that reduce water loss. ○​ Advantage: Seeds enable survival in harsher climates, and the ability to reproduce without water allows for greater geographic distribution. ​ (d) Angiosperms: ○​ Adaptations: Flowers for pollination, fruit for seed dispersal, and efficient vascular tissues. ○​ Advantage: Increased reproductive success through pollinator attraction and seed dispersal mechanisms (e.g., wind, animals). 7. Major Limitations in the Terrestrial Environment for Each Major Plant Group ​ Mosses: ○​ Limitation: Dependence on water for reproduction (spores must swim to fertilize eggs). ​ Seedless Vascular Plants: ○​ Limitation: Still reliant on water for reproduction, as they reproduce via spores. ​ Gymnosperms: ○​ Limitation: Limited to colder or drier environments due to their reliance on wind for pollination and seed dispersal. ​ Angiosperms: ○​ Limitation: Invasive species can sometimes limit the spread, but overall, angiosperms are highly adapted for diverse terrestrial environments. 8. Comparison of Monocots and Eudicots ​ Monocots: ○​ One cotyledon (seed leaf). ○​ Parallel-veined leaves. ○​ Vascular bundles scattered throughout the stem. ○​ Flower parts in multiples of three. ○​ Examples: grasses, lilies, orchids. ​ Eudicots: ○​ Two cotyledons. ○​ Netted or branching-veined leaves. ○​ Vascular bundles in a circle or ring. ○​ Flower parts in multiples of four or five. ○​ Examples: roses, sunflowers, beans. Slide 6 Biology 1100 Test 1 1. Comparison of Primary and Secondary Cell Walls in Vascular Plants ​ Location: ○​ Primary Cell Wall: Found in all plant cells, especially in young, growing cells. It is present in all cells before secondary growth begins. ○​ Secondary Cell Wall: Formed in some plant cells (usually mature cells) after the primary wall has been established, typically found in cells like xylem and sclerenchyma. ​ Structure: ○​ Primary Cell Wall: Made of cellulose fibers, hemicellulose, pectin, and some proteins. It is flexible, allowing for cell expansion during growth. ○​ Secondary Cell Wall: Consists of lignin (a complex polymer that provides rigidity) and cellulose. It is thicker, stronger, and more rigid compared to the primary wall. ​ Function: ○​ Primary Cell Wall: Provides structural support for the cell, allows cell growth, and provides flexibility. ○​ Secondary Cell Wall: Provides added strength, rigidity, and protection, often aiding in the prevention of pathogen entry. It is especially important in cells that need to withstand pressure (e.g., in vascular tissues like xylem). 2. Turgor Pressure and Its Contribution to Support in Plants ​ Turgor Pressure: The pressure exerted by the cell membrane against the cell wall due to the water intake in the vacuole. ​ Contribution to Support: Turgor pressure helps maintain the structural integrity and rigidity of plant cells. It ensures that plant cells stay firm, allowing non-woody parts of the plant (like leaves) to remain erect. Without sufficient turgor pressure, plant cells would collapse, leading to wilting. 3. Structure of Cell Types and Their Functions in Vascular Plants ​ (a) Epidermis: ○​ Structure: The outermost layer of cells, typically one cell layer thick, with a waxy cuticle. ○​ Function: Protection against water loss, pathogens, and physical damage. The cuticle helps reduce water evaporation. ​ (b) Parenchyma: ○​ Structure: Thin-walled, living cells, often with large central vacuoles. ○​ Function: Metabolic functions, including photosynthesis (in leaves) and storage (in roots). They are flexible and can divide to repair tissue. ​ (c) Collenchyma: ○​ Structure: Living cells with unevenly thickened cell walls.  ○​ Function: Provides flexible support to growing parts of the plant, such as young stems and petioles. ​ (d) Sclerenchyma: ○​ Structure: Dead cells with thick, lignified secondary walls. ○​ Function: Provides rigid support and strength, especially in mature tissues like vascular bundles and seed coats. ​ (e) Cambium: ○​ Structure: A layer of undifferentiated cells that can divide and form new tissues (vascular cambium and cork cambium). ○​ Function: Responsible for secondary growth, contributing to the thickening of stems and roots. ​ (f) Xylem (Tracheids and Vessel Elements): ○​ Structure: Xylem consists of tracheids (long, tapered cells) and vessel elements (shorter, wider cells with perforated end walls). ○​ Function: Transport of water and dissolved minerals from roots to the rest of the plant. ​ (g) Phloem (Sieve Tubes and Companion Cells): ○​ Structure: Phloem consists of sieve tube elements (long tubes with perforated ends) and companion cells (which support the sieve tubes). ○​ Function: Transport of sugars and other organic molecules throughout the plant. 4. Structure and Functions of the Root System and Shoot System ​ Root System: ○​ Structure: Composed of roots, including primary roots and lateral roots. It typically includes a root cap for protection and root hairs for increased surface area. ○​ Function: Anchors the plant, absorbs water and nutrients from the soil, stores carbohydrates, and transports them to other parts of the plant. ​ Shoot System: ○​ Structure: Composed of stems, branches, leaves, and flowers. ○​ Function: Supports the plant’s reproductive organs (flowers), conducts photosynthesis (in leaves), and transports water, nutrients, and sugars (through vascular tissues). 5. Meristematic Tissue and Its Significance to Primary Growth ​ Location: Meristematic tissue is found at the tips of roots and shoots (apical meristems) and in vascular and cork cambium (lateral meristems). ​ Significance: Meristematic tissue is composed of undifferentiated cells that divide and differentiate to form all other plant tissues. It is responsible for primary growth, which increases the length of roots and shoots. 6. Secondary Growth and Its Contribution to Mechanical Support  ​ Secondary Growth: The growth that occurs after the initial formation of the plant. It involves the thickening of stems and roots due to the activity of the vascular cambium (producing secondary xylem and phloem) and cork cambium (producing bark). ​ Contribution to Mechanical Support: Secondary growth increases the girth and strength of the plant, allowing it to support larger structures and withstand environmental pressures (wind, weight). The increased production of lignin in secondary xylem strengthens the plant. 7. Adaptations for Terrestrial Environments ​ (a) Roots: Roots anchor the plant and absorb water and essential nutrients from the soil. They also store carbohydrates and provide support. ​ (b) Leaves: Leaves are specialized for photosynthesis. Their large surface area allows for maximum light absorption, and their structure is adapted to minimize water loss (e.g., stomata, waxy cuticle). ​ (c) Xylem: Xylem has lignin in its cell walls, providing structural support and allowing for the efficient transport of water and minerals through the plant. ​ (d) Phloem: Phloem transports sugars and other organic compounds produced in photosynthesis. Its ability to move nutrients is essential for long-distance transport within the plant. ​ (e) Cuticle: The cuticle is a waxy layer on the surface of leaves and stems that reduces water loss, helping to conserve moisture in terrestrial environments. ​ (f) Stomata: Stomata are pores in the leaf surface that regulate gas exchange (CO₂ in, O₂ out) and water loss. The ability to open and close helps the plant manage water retention while obtaining necessary gases for photosynthesis. Slide 7 Biology 1100 Test 1 1. Distinguishing Characteristics of Animals - Multicellular: Animals are multicellular organisms with specialized cells that work together. - Heterotrophic: They obtain their food by consuming other organisms (either plants or animals). - Movement: Most animals have the ability to move at some point in their life cycle, usually through muscle tissue and nervous systems. - Lack of cell walls: Unlike plants, animals don’t have rigid cell walls; they have flexible cell membranes. - Nervous System: Most animals have a nervous system that allows them to sense and respond to their environment. - Reproduction: Most animals reproduce sexually, although some can reproduce asexually. 2. Levels of Body Complexity Among Animal Phyla - Tissues: The simplest level of organization, where groups of similar cells perform specific functions (e.g., in sponges, which lack organs). - Organs: In animals with organs, groups of tissues combine to perform specific tasks (e.g., hearts, lungs). - Organ Systems: Higher complexity is seen in animals with organ systems (e.g., digestive system, nervous system), where organs work together to perform broader functions (e.g., in humans). 3. Hypothesis for the Origin of Animals from Ancient Protists The hypothesis suggests that animals evolved from a group of ancient, multicellular protists called *choanoflagellates*. These protists share several key features with animals, including: - A collar of microvilli that can capture food particles. - Similarities in genes related to cell signaling, adhesion, and development. The hypothesis posits that over time, a colony of these protists may have developed specialization of cells, eventually leading to the formation of early animal forms. 4. Features of Evolution in Animal Body Plans Radial vs. Bilateral Symmetry: - Radial symmetry: Body parts are arranged around a central axis (e.g., jellyfish). - Bilateral symmetry: Body has a distinct left and right side, typically with a head region (e.g., humans, worms). Gut with One vs. Two Openings: - One opening (incomplete digestive system): Food enters and exits through the same opening (e.g., cnidarians, flatworms). - Two openings (complete digestive system): Food enters through the mouth and exits through the anus (e.g., humans, most animals). Acoelomates vs. Coelomates: - Acoelomates: Animals without a body cavity (e.g., flatworms). - Coelomates: Animals with a true body cavity (coelom) that is lined with mesoderm (e.g., annelids, chordates). - Differences in Structural Complexity: Some animals have simple body plans with minimal organ systems (e.g., sponges), while others have complex systems (e.g., humans). 5. Coelom Definition & Phyla - Coelom: A body cavity that is fully lined by mesoderm tissue, providing space for organs to grow and move independently of the body wall. - Phyla with Coeloms: Examples include annelids, mollusks, arthropods, echinoderms, and chordates. 6. Gastrovascular Cavity vs. Alimentary Canal - Gastrovascular Cavity: A simple digestive cavity with a single opening used for both ingestion and egestion (e.g., cnidarians, flatworms). - Alimentary Canal: A more complex digestive tract with two openings (mouth and anus) that allows for more efficient digestion and absorption (e.g., most animals). 7. Hydrostatic Skeleton, Exoskeleton, Endoskeleton - Hydrostatic Skeleton: A fluid-filled body cavity that provides support (e.g., earthworms, cnidarians). - Exoskeleton: A hard outer structure that protects and supports the body (e.g., arthropods, mollusks). - Endoskeleton: An internal skeleton made of bone or cartilage that provides support and structure (e.g., vertebrates) 8. Phylogenetic Tree of Animal Phyla A phylogenetic tree organizes animal phyla based on evolutionary relationships. It shows the branching patterns of animal evolution from a common ancestor, usually starting with simpler, less complex forms like sponges and progressing to more complex forms like humans and other vertebrates. 9. Major Characteristics of Animal Phyla - (a) Porifera: Sponges, simple body plan, no true tissues, filter feeders. - (b) Cnidaria: Jellyfish, corals, radial symmetry, cnidocytes (stinging cells). - (c) Platyhelminthes: Flatworms, bilateral symmetry, no body cavity, simple organ systems. - (d) Nematoda: Roundworms, bilateral symmetry, complete digestive system, pseudocoelomates. - (e) Mollusca: Mollusks (snails, clams, octopuses), soft bodies, most have hard shells, coelomates. - (f) Annelida: Segmented worms (earthworms, leeches), segmented body, coelomates, complete digestive system. - (g) Arthropoda: Insects, arachnids, crustaceans, exoskeletons, segmented bodies, jointed appendages. - (h) Echinodermata: Starfish, sea urchins, radial symmetry (as adults), endoskeleton, water vascular system. - (i) Chordata: Vertebrates and some invertebrates, possess a notochord, dorsal nerve cord, pharyngeal slits, and post-anal tail at some stage in development. 10. Classes of Vertebrates - a) Ray-finned (Bony) Fish: Fish with a skeleton made of bone, fins supported by thin bony rays (e.g., goldfish). - (b) Amphibians: Vertebrates that live both in water and on land, typically have moist skin (e.g., frogs, salamanders). -(c) Reptiles (Including Birds): Cold-blooded vertebrates with scaly skin, most lay eggs; birds are warm-blooded reptiles (e.g., snakes, turtles, birds). -(d) Mammals: Warm-blooded vertebrates with hair/fur, mammary glands that produce milk, and live births (e.g., humans, whales, bats). Slide 8 Biology 1100 Test 1 1. Definitions: - (a) Ingestion: The process of taking in food or liquids through the mouth. This is the first step in the digestive process. - (b) Digestion: The breakdown of food into smaller, absorbable components (e.g., carbohydrates into sugars, proteins into amino acids). It can occur both mechanically (chewing) and chemically (enzymes). - (c) Absorption: The process by which digested nutrients (like amino acids, sugars, fatty acids) are taken up into the bloodstream or lymphatic system through the walls of the small intestine. - (d) Elimination: The process of expelling indigestible substances and waste products from the body, typically in the form of feces. 2. Extracellular Digestion vs. Intracellular Digestion - Extracellular Digestion: Digestion occurs outside of cells, in a digestive cavity or gut. This is common in most animals. Enzymes are secreted into a cavity where food is broken down into smaller molecules that can be absorbed (e.g., in the stomach and intestines). - Intracellular Digestion: Digestion occurs within individual cells. Organisms with this system engulf food particles by phagocytosis, then digest them within vacuoles (e.g., in sponges or some protozoans). 3. Evolutionary Significance of the Trend from Intracellular to Extracellular Digestion The shift from intracellular to extracellular digestion represents a major evolutionary advancement for several reasons: - Efficiency: Extracellular digestion allows for the processing of larger food particles, increasing the range of possible food sources and making digestion more efficient. - Specialization: This allows the specialization of different parts of the digestive system, increasing the overall efficiency of nutrient extraction. Different areas of the gut can perform different roles (e.g., mechanical breakdown, enzymatic breakdown, absorption). - Increased Size: Larger organisms require more energy, and extracellular digestion allows them to process larger quantities of food more effectively. - Adaptation: It allows for the development of complex, multi-step digestive processes that are more suited to varying diets and environments. 4. Digestive Systems of Porifera, Cnidaria, and Annelida - Porifera (Sponges): - Digestion: They have intracellular digestion, where food particles are captured by collar cells (choanocytes) and engulfed. The digested food is processed inside the cell. - Special Feature: No digestive cavity; food is filtered through the body by water currents. - Cnidaria (Jellyfish, Corals): - Digestion: They possess an incomplete digestive system with a single opening (gastrovascular cavity). Digestion begins extracellularly in the cavity, where enzymes break down food, followed by absorption by the cells lining the cavity. - Special Feature: Radial symmetry, with a central body cavity that serves both as the digestive space and a circulatory system. - Annelida (Earthworms, Leeches): - Digestion: They have a complete digestive system (two openings: mouth and anus) with extracellular digestion. Food is ingested through the mouth, processed in specialized regions (e.g., crop, gizzard, intestine), and absorbed in the intestine. -Special Feature: Segmentation of the digestive system allows for more effective movement of food and more specialized regions for different digestive functions. 5. Digestive Organs in Humans Location, Structure, and Function of Digestive Organs: 1. Oral Cavity: - Location: Mouth. - Structure: Contains teeth, tongue, and salivary glands. - Function: Begins the process of mechanical digestion (chewing) and chemical digestion (saliva contains enzymes like amylase to break down starches). 2. Esophagus: - Location: Connects the oral cavity to the stomach. - Structure: A muscular tube. - Function: Transports food from the mouth to the stomach via peristalsis (wave-like muscle contractions). 3. Stomach: - Location: Left side of the abdomen, below the diaphragm. - Structure: A muscular, acidic sac lined with mucous membranes and glands that secrete digestive enzymes and hydrochloric acid. - Function: Secretes gastric juices to break down food, particularly proteins. It also churns food mechanically to mix with digestive fluids. 4. Small Intestine: - Location: Below the stomach.  - Structure: Divided into three parts: duodenum, jejunum, and ileum. Lined with villi and microvilli to increase surface area. - Function: Major site for digestion and nutrient absorption. Enzymes from the pancreas and bile from the liver aid digestion, and the nutrients are absorbed through the villi into the bloodstream. 5. Accessory Organs: - Liver: Produces bile to emulsify fats and detoxifies various metabolic products. - Gallbladder: Stores and concentrates bile from the liver and releases it into the small intestine to aid in fat digestion. - Pancreas: Secretes digestive enzymes (amylase, lipase, proteases) into the small intestine and bicarbonate to neutralize stomach acid. 6. Large Intestine: - Location: Surrounds the small intestine. - Structure: Includes the cecum, colon, rectum, and anus. - Function: Absorbs water and salts from the material that has not been digested, forming solid waste. It also houses beneficial bacteria involved in fermenting undigested food. Relating Structure to Function: - Oral Cavity: Teeth and tongue facilitate mechanical breakdown, while saliva begins chemical digestion. - Esophagus: Muscular walls help move food quickly to the stomach via peristalsis. - Stomach: Thick muscular walls churn food and secrete hydrochloric acid and enzymes to begin protein digestion. - Small Intestine: Villi and microvilli increase surface area for absorption. The division into parts allows for efficient digestion and absorption at different stages. - Liver, Gallbladder, Pancreas: These accessory organs release digestive enzymes and bile, crucial for breaking down fats, proteins, and carbohydrates. - Large Intestine: Its broader diameter and water-absorbing capacity help compact waste into solid form, ready for excretion. 6. Digestive Systems of Herbivores vs. Carnivores - Herbivores: - Diet: Primarily plant-based foods, which are harder to digest due to cellulose in plant cell walls. - Digestive System: - Longer intestines (especially the cecum and colon) for longer fermentation and absorption of nutrients from plants. - Specialized enzymes (e.g., cellulase) or symbiotic bacteria to break down cellulose. - Herbivores like cows have **ruminants** (four-chambered stomachs) to help break down plant matter over multiple fermentation stages. - Carnivores:  - Diet: Meat-based foods, which are easier to digest due to their simpler protein structures. - Digestive System: - Shorter digestive tracts, as meat is easier to break down and absorb. - Strong acidic environments and enzymes that can efficiently break down proteins and fats. - Teeth and jaws designed for tearing and crushing meat (e.g., carnassial teeth in carnivorous mammals). Key Differences: - Length of Digestive Tract: Herbivores have longer intestines and specialized fermentation chambers (like the rumen) to process plant matter, while carnivores have shorter, more acidic digestive systems. - Enzyme Systems: Herbivores rely more on bacteria for digestion (especially of cellulose), while carnivores’ digestive enzymes are focused on breaking down proteins and fats. Slide 9 Biology 1100 Test 1 1. Definitions ​ Ecology: The scientific study of the interactions between organisms and their environment, focusing on the distribution and abundance of organisms and how they affect and are affected by each other and their surroundings. ​ Community: A group of different species living in the same area, interacting with one another. Communities include all the biotic (living) factors in an environment. ​ Ecosystem: A biological community of interacting organisms (plants, animals, microbes) and their physical environment (air, water, soil). It includes both the biotic and abiotic factors and how they interact within a specific area. ​ Biome: A large geographic biotic unit characterized by specific climate conditions, plant types, and animal species. Biomes are categorized based on the climate and dominant vegetation, such as forests, grasslands, or deserts. 2. Four Types of Terrestrial Biomes and Climatic Factors Influencing Their Distribution ​ (a) Tundra (Arctic and Alpine): ○​ Climate: Cold temperatures, short growing seasons, and low precipitation. Permafrost is common in the Arctic tundra. ○​ Vegetation: Low-growing plants such as mosses, lichens, grasses, and small shrubs. ○​ Distribution: Found in polar regions and high mountain tops (alpine tundra). ○​ Climatic Influence: Low temperatures and short daylight hours limit plant growth and biological activity. Permafrost restricts root growth in the Arctic tundra. ​ (b) Taiga (Northern Coniferous Forest): ○​ Climate: Cold, with long winters and short, cool summers. Precipitation is moderate, mostly as snow. ○​ Vegetation: Dominated by coniferous trees like pines, spruces, and firs. ○​ Distribution: Found just south of the tundra in the Northern Hemisphere, across North America, Europe, and Asia. ○​ Climatic Influence: Long winters and cold temperatures favor coniferous trees that are adapted to conserve water and withstand cold, while a short growing season limits the variety of plant life. ​ (c) Temperate Deciduous Forest: ○​ Climate: Moderate temperatures, with four distinct seasons, including cold winters and warm summers. Precipitation is evenly distributed throughout the year. ○​ Vegetation: Dominated by broadleaf trees like oaks, maples, and beeches that shed their leaves in fall. ○​ Distribution: Found in temperate regions of the world, such as eastern North America, much of Europe, and parts of Asia.  ○​ Climatic Influence: The moderate climate supports a variety of deciduous trees, and the seasonal changes in temperature allow for nutrient cycling through leaf drop and decomposition. ​ (d) Desert: ○​ Climate: Very low precipitation, high temperatures during the day, and cold nights. ○​ Vegetation: Cacti, succulents, and drought-resistant plants that conserve water. ○​ Distribution: Found in regions with little rainfall, such as North Africa, the Middle East, southwestern U.S., and Australia. ○​ Climatic Influence: Low precipitation limits plant growth. The extreme temperatures of day and night create challenges for both plants and animals to conserve water and energy. 3. Distinction Between Organic and Inorganic Compounds ​ Organic Compounds: Compounds primarily made up of carbon atoms bonded to hydrogen and usually oxygen, nitrogen, and other elements. These compounds are associated with living organisms (e.g., carbohydrates, proteins, lipids, nucleic acids). ​ Inorganic Compounds: Compounds that do not contain carbon-hydrogen bonds. These include substances like water, salts, acids, and bases that are not derived from living organisms. 4. Two Major Functions of Organic Compounds and Sources of Building Blocks ​ Functions: ○​ Energy Storage and Release: Organic compounds like carbohydrates and lipids store and release energy for organisms. ○​ Structural Support: Proteins and cellulose provide structural support to cells and tissues. ​ Building Blocks: ○​ Autotrophs (Plants, Algae, Cyanobacteria): Obtain building blocks (carbon, nitrogen, oxygen, etc.) from the environment through processes like photosynthesis. Carbon is fixed from CO₂, and nitrogen is absorbed from the soil or atmosphere. ○​ Heterotrophs (Animals, Fungi): Obtain organic compounds by consuming plants, other animals, or decomposing matter. They obtain carbon and nitrogen from their food sources. 5. Biogeochemical Cycle and Its Main Components ​ Biogeochemical Cycle: The movement of elements (such as carbon, nitrogen, phosphorus) through biological, geological, and chemical processes. These cycles describe how elements are recycled in ecosystems. ​ Main Components: ○​ Biotic Components: Organisms that contribute to the cycling of elements (e.g., plants, animals, decomposers).  ○​ Abiotic Components: Non-living elements of the environment (e.g., air, water, soil). ○​ Processes: The physical, chemical, and biological processes that move elements through the ecosystem (e.g., respiration, photosynthesis, decay, precipitation, evaporation). 6. Significance of Carbon and Nitrogen to Living Organisms and Their Cycling ​ Carbon: ○​ Significance: Carbon is the building block of organic molecules such as carbohydrates, proteins, and fats, essential for life. It is also a critical component of the energy cycle in organisms. ○​ Cycling: Carbon is cycled through the atmosphere (as CO₂), the ocean, and terrestrial ecosystems. It enters the food chain through photosynthesis and is released back into the atmosphere through respiration, decay, and combustion. ​ Nitrogen: ○​ Significance: Nitrogen is a key component of amino acids, proteins, and nucleic acids (DNA and RNA). ○​ Cycling: Nitrogen enters ecosystems through nitrogen fixation (by nitrogen-fixing bacteria) or from atmospheric deposition. It is used by plants, then passed through the food chain. Nitrogen is returned to the atmosphere through denitrification and can be recycled in the soil by decomposers. 7. Human Impacts on Biogeochemical Cycles and Ecosystems ​ Carbon Cycle: ○​ Human activities like burning fossil fuels, deforestation, and industrial processes increase CO₂ levels in the atmosphere, contributing to climate change. ​ Nitrogen Cycle: ○​ The use of synthetic fertilizers in agriculture releases excess nitrogen into ecosystems, causing nutrient pollution and disrupting natural nitrogen cycling. This can lead to algal blooms and dead zones in water bodies. ​ Other Impacts: ○​ Habitat Destruction: Deforestation, urbanization, and agriculture fragment ecosystems, reducing biodiversity and disrupting nutrient cycles. ○​ Pollution: Industrial waste, chemicals, and plastics disrupt ecosystems and harm species. ○​ Overexploitation: Overfishing, hunting, and harvesting resources at unsustainable rates lead to species extinction and ecosystem degradation. These human activities alter natural cycles, affecting the health of ecosystems and the planet's overall sustainability. Slide 10 Biology 1100 Test 1 1. Definition of Trophic Level and Identification of Members ​ Trophic Level: The position an organism occupies in a food chain, based on its source of energy. ​ Members of Trophic Levels: ○​ (a) Producer: Organisms that make their own food through photosynthesis or chemosynthesis. They form the first trophic level and provide energy for all other organisms in an ecosystem. Examples: plants, algae, phytoplankton. ○​ (b) Consumer: ​ Primary Consumer: Herbivores that feed on producers. Examples: deer, rabbits, insects. ​ Secondary Consumer: Carnivores that eat primary consumers. Examples: frogs, small fish. ​ Tertiary Consumer: Carnivores that eat secondary consumers. Examples: hawks, large fish, lions. ​ Quaternary Consumer: Top predators that eat tertiary consumers, often at the top of the food chain. Examples: killer whales, human apex predators. ○​ (c) Herbivore: Animals that eat plants (producers). Examples: cows, caterpillars, zebras. ○​ (d) Carnivore: Animals that eat other animals. Examples: wolves, lions, eagles. ○​ (e) Omnivore: Animals that eat both plants and animals. Examples: humans, bears, raccoons. ○​ (f) Decomposer: Organisms that break down dead organic material, recycling nutrients back into the ecosystem. Examples: fungi, bacteria, earthworms. 2. Distinction Between Food Chain and Food Web ​ Food Chain: A linear sequence of organisms in an ecosystem where each organism is eaten by the next. It shows the direct flow of energy from one organism to another. Example: grass → rabbit → fox. ​ Food Web: A complex network of interconnected food chains within an ecosystem. It more accurately represents the feeding relationships in an ecosystem, showing how different species are interlinked. Example: A rabbit might be eaten by a fox, but it might also be eaten by an eagle. 3. Energy Flow and Chemical Cycling in an Ecosystem ​ Energy Flow: Energy flows in one direction through an ecosystem—starting with producers (via photosynthesis), moving through consumers, and eventually to decomposers. Energy is lost as heat at each trophic level due to metabolism (second  law of thermodynamics). Only about 10% of the energy is passed to the next trophic level. ​ Chemical Cycling: Unlike energy, chemicals like carbon, nitrogen, and phosphorus cycle through the ecosystem, moving between organisms, the soil, water, and atmosphere. Through processes like decomposition, photosynthesis, and respiration, these chemicals are reused by producers and consumers. ​ Common Pathways: ○​ Carbon Cycle: CO₂ is absorbed by plants, passed through the food chain, and returned to the atmosphere by respiration and decomposition. ○​ Nitrogen Cycle: Nitrogen is fixed by bacteria, taken up by plants, passed to herbivores and carnivores, and returned to the soil by decomposers or denitrifying bacteria. 4. Limited Number of Trophic Levels (Trophic Efficiency) ​ Trophic Efficiency: The percentage of energy that is transferred from one trophic level to the next. Typically, only about 10% of the energy at one level is passed on to the next level, while the rest is used for metabolism or lost as heat. This inefficiency limits the number of trophic levels in a food web, as the energy available for higher trophic levels becomes too low to sustain large populations. 5. Energy Pyramid (Pyramid of Net Production) ​ Energy Pyramid: A graphical representation of the amount of energy available at each trophic level in an ecosystem. The pyramid shows that energy decreases as you move up the trophic levels, with producers at the base providing the most energy, and each successive level receiving less energy due to trophic inefficiency. ​ Shape: The pyramid is typically broad at the base (producers) and narrows as you move up through primary consumers, secondary consumers, and so on. This shape reflects the decrease in energy available at higher trophic levels. 6. Intraspecific vs. Interspecific Interactions in a Community ​ Intraspecific Interaction: Interactions that occur between individuals of the same species. These include competition for resources like food, mates, and territory. ​ Interspecific Interaction: Interactions that occur between individuals of different species. These include predation, competition, mutualism, and other relationships that involve different species coexisting. 7. Four Major Types of Interspecific Interactions ​ (a) Competition: Occurs when individuals or species vie for the same limited resources (e.g., food, territory). Example: Two species of birds fighting for the same nesting sites. ​ (b) Predation: One organism (the predator) kills and eats another (the prey). Example: A lion hunting and eating a zebra.  ​ (c) Mutualism: Both species benefit from the interaction. Example: Pollinators (like bees) transfer pollen between flowers while feeding on nectar, benefiting both the plant and the pollinator. ​ (d) Commensalism: One species benefits, while the other is neither helped nor harmed. Example: Barnacles attached to the shell of a turtle. The barnacles benefit from access to more water flow while the turtle is unaffected. 8. Keystone Species and the Impact of Their Removal ​ Keystone Species: A species whose presence and role in an ecosystem have a disproportionate effect on the structure of the community. Removing a keystone species can lead to significant changes or collapse of the ecosystem. ​ Example: Sea otters are a keystone species in kelp forests. They control sea urchin populations that graze on kelp. Without otters, urchin numbers explode, and kelp forests can be destroyed. 9. Examples of Human Impact on Ecosystems and Their Implications ​ Deforestation: The removal of trees for agriculture, urbanization, and logging leads to loss of biodiversity, disrupted water cycles, and increased carbon emissions. ​ Pollution: Chemical pollutants in the air, water, and soil can harm living organisms, disrupt ecosystems, and lead to dead zones in oceans (e.g., eutrophication from excess nitrogen and phosphorus). ​ Climate Change: Human activities, such as burning fossil fuels, contribute to global warming. This shifts climate patterns, affecting species distribution, migration patterns, and ecosystem services. ​ Overfishing: Depleting fish populations leads to imbalances in marine ecosystems, affecting food webs and the economy of coastal communities. These human impacts can result in long-term damage to ecosystems, causing irreversible changes in biodiversity, resource availability, and ecosystem function.