Biology Exam Review - Classification of Living Things PDF

Biology 11: Unit 1 Classification of living things (Lesson 1) -​ Biodiversity is the variety of life on Earth -​ Includes every living thing, multicellular or unicellular -​ Requires an organization system -​ Classification of living things: Taxonomy Classifying Species -​ Bi...

Biology 11: Unit 1 Classification of living things (Lesson 1) -​ Biodiversity is the variety of life on Earth -​ Includes every living thing, multicellular or unicellular -​ Requires an organization system -​ Classification of living things: Taxonomy Classifying Species -​ Biological Species -​ Group of organisms that can interbreed, and produce fertile offspring -​ Labradoodle is fertile, meaning the labrador and poodle are the same species -​ Zorses are infertile -​ Horses and zebras are not the same species -​ Considered a hybrid Three Levels of Biodiversity -​ Genetic Diversity -​ The variety of genes in an organism, within one species -​ Species Diversity -​ Number of each species, and variety of different species in an ecosystem -​ Species Interactions -​ Organisms relying on another species for survival -​ Ecological Diversity -​ Variation of biological communities in terrestrial/aquatic ecosystems -​ Biotic and abiotic factors Classification -​ Scientists attempt to order the natural world, by grouping and classifying organisms -​ As technology improves, so do our systems Darwin’s Theory of Evolution 1.​ Organisms produce more offspring than can survive. Of the offspring that do survive, many will never reproduce. 2.​ Because more organisms are produced than can survive, there is intense competition for limited resources, such as food, water, and shelter. 3.​ Every organism that exists today is because of what developed through evolution  4.​ Individuals that are best suited to their environment survive, reproduce and pass their traits on to their offspring. Other organisms that are less suited often die or will not be reproductively competitive. -​ Process of “Natural Selection” that causes evolution on earth -​ The species that are alive today, descended with modification from species that lived in the past -​ For 3.5 Billion years, life has been changing on earth -​ Natural selection has led to diversity within organisms -​ To study the scientist must give each organism a name and sort them into groups -​ Called Taxonomy Taxonomy -​ Branch of biology that classifies organisms, and assigns them a name Early Attempts of Classification -​ Organisms were first classified over 2000 years ago by Aristotle -​ Sorted them into 2 groups -​ Animals -​ Land dwellers -​ Water dwellers -​ Air dwellers -​ Plants -​ Herbs -​ Shrubs -​ Trees -​ By the 15th-16th centuries, it became obvious that there were problems with this system -​ Many organisms were placed in groups they had no relation to -​ Use of common names was confusing -​ Catfish -​ Jellyfish -​ Shellfish -​ Many new organisms were being discovered, and needed to be classified -​ In response, Carolus Linnaeus developed a better system that we still use today Binomial Nomenclature -​ System Linnaeus created  -​ Based on structural similarity -​ Organisms that looked alike, were most closely related -​ System placed an organism in a particular group, and assigned it a scientific name -​ Consists of 2 parts -​ Linnaeus divided all organisms into large groups called kingdoms -​ Originally 2 kingdoms -​ Plant and animal kingdom -​ Kingdoms were subdivided into smaller groups -​ Each subdivision of a kingdom was called phylum for animals, or division for plants -​ Subdivided until he had 7 levels of classification -​ Kingdom -​ Phylum/Division -​ Class -​ Order -​ Family -​ Genus -​ Species -​ Placed in species if they can mate and produce fertile offspring -​ Contains one type of organism -​ Later on, a level above kingdom was added, called “Domain” -​ Domain -​ Kingdom -​ Phylum -​ Class -​ Order -​ Family -​ Genus -​ Species -​ Domain = broadest -​ Species = most specific Domains -​ Three domains of life -​ Bacteria -​ Archaea -​ Eukarya -​ Bacteria + Archaea are both single celled organisms  -​ Eukarya includes all organisms with complex, multicellular structures Rules for Binomial Nomenclature -​ Scientific name consists of two words -​ Genus and species -​ All scientific names are in latin -​ The genus name is always capitalized -​ The species name is never capitalized -​ The two names are always written in italics or underlined -​ No two organisms can have the same name -​ Examples: -​ Macaca fuscata -​ Sula nebouxii​ Diversity of Living Things (Lesson 2) Modern Taxonomy: Phylogeny -​ Phylogeny: The evolutionary history of an organism -​ Modern taxonomists now consider the phylogeny of an organism when classifying it -​ To show the evolutionary relationship between different groups of organisms, scientists make phylogenetic trees -​ Phylogenetic tree -​ Family tree that shows the evolutionary relationships thought to exist among different groups of organisms -​ Traditionally, the morphology (structure) if the organism was the basis for it’s classification -​ Modern taxonomy takes into account other types of evidence -​ Morphology -​ Cellular Organization -​ Evolutionary Relationships -​ Embryological Similarities -​ Biochemical Similarities -​ Genetic Similarities Morphology (Structural similarities) -​ Morphology is classification based on the structures and organism has -​ This was the basis of Linnaeus’ system of classification -​ Color and size are the least important​ -​ Structure Types: -​ Homologous Structures -​ Structures in different species that are similar because of common ancestry -​ Example: -​ The bones found in the wing of a bird, the wing of a bat, the forearm of a human, and the flipper of a whale are homologous to one another -​ Analogous Structures -​ Structures in different species that are similar in function, but not in structure -​ Not derived from a common ancestor -​ Example: -​ Wing of a bird and wing of a butterfly have the same function, but nothing in common in their structure -​ Vestigial Structures -​ Structure reduced in size, and seem to be “left over” from a previous ancestor -​ Examples: -​ Human appendix, and hip bone in whales​ -​ The more homologous structures two organisms share, the more closely related they are thought to be -​ The fossil record gives us many clues of the morphology, but it is incomplete -​ Other lines of evidence must be used -​ Cellular Organization -​ Similarity in cell structures provides evidence that organisms may be related -​ Examples: -​ What kinds of plastids are present? -​ Does the cell have a nucleus? -​ Is there a cell wall? -​ What is the cell wall made of?​ -​ Evolutionary Relationships -​ Scientist now group organisms by phylogeny -​ Fossils show that organisms alive today, are similar to organisms that are now extinct -​ Example:  -​ 25 dog breeds come from a wolf-like ancestor​ -​ Biochemical Similarities -​ Similarities in chemical compounds found in cells can be used as evidence to show relationships between organisms -​ A comparison between the organisms serves as a “molecular clock” -​ Simple mutations occur all the time, causing slight differences in the DNA and Proteins being built -​ When the proteins of two different organisms are compared, the number of differences in amino acid sequences is a clue as to how long ago they diverged from a common ancestor​ -​ Genetic Similarities -​ Two organisms that don’t resemble each other may still be related -​ Similar genes in their DNA -​ Example: -​ Humans have code for building protein called myosin -​ Primary component for building muscles -​ Yeasts, which have no muscles, have the same gene -​ Used to move materials around the inside of the cell -​ The more similar the DNA sequence of two species, the more recently they shared a common ancestor -​ The less similar the DNA sequence, the more diverged they are -​ Embryological Similarities -​ Similarities in embryological development, are evidence of phylogenetic relationships -​ Some organisms show no similarities as adults, but are very similar as embryos -​ Example -​ An amnion is a fluid filled sac that surrounds the embryos of some vertebrates -​ Embryos of fish and amphibians lack one -​ Embryos of reptiles, birds and mammals have an amnion -​ Because the have a shared embryological structure, reptiles, birds, and mammals are grouped and referred to as amniotes Cladistics -​ Relatively new method of classifying organisms -​ Cladistics identifies the characteristics of organisms that are “evolutionary innovations” -​ New characteristics that evolved over time -​ Shared characters + Derived characters to establish evolutionary relationships -​ Shared Character -​ A feature that all members of a group have in common -​ Examples: -​ Feathers in birds -​ Hair in mammals -​ Derived character -​ A feature that evolved in a group -​ Example: -​ Feathers in a bird -​ Birds are the only animals to have feathers, it’s assumed that feathers evolved in the bird group -​ Not inherited from a distant ancestor -​ Shared derived characters are evidence of common ancestry between organisms that share them -​ Organisms that share one or more common ancestor, most likely inherited those from a common ancestor -​ Clades -​ The Term is used to describe a group of organisms that includes an ancestor, and all its descendants -​ Do not use traditional Linnaean category names, such as phylum, class or order -​ The relationship between the organisms in a clade, can be shown using a cladogram -​ Cladogram: -​ A diagram that shows the evolutionary relationship among a group of organisms -​ Constructing a Cladogram -​ A cladogram deliberately includes an organism that is only distantly related to the other organisms -​ The “Out-Group” -​ Serves as a basis of comparison between the other organisms​ ​ ​ ​ Classification of Living Things: Lesson 3 Kingdoms and Domain -​ As new discoveries were made, the systems of classification had to be changed -​ Since Linnaeus, many changes have been made -​ 1700s: Plantae and Animalia -​ Late 1800s: Protista, Plantae, and Animalia -​ 1950s: Monera, Protista, Fungi, Plantae and Animalia -​ 1990s: Archae-bacteria, Eubacteria, Protista, Fungi, Plantae and Animalia -​ 5, and 6 kingdom system is evidence that all living organisms naturally fell into three broad groups -​ 3-domain system -​ Domains are the highest taxonomic level -​ Domains -​ Archaea -​ Archaebacteria -​ Bacteria -​ Eubacteria -​ Eukarya -​ Protista -​ Plantae -​ Fungi -​ Animalia -​ Comparison -​ Domain: Bacteria -​ Kingdom: Eubacteria -​ Cell Type: Prokaryotic -​ Cell Structures: Thick and rigid cell walls composed of peptidoglycans -​ Cell Organization: Unicellular -​ Food Getting: Autotrophs and heterotrophs -​ Examples: Strep, Staph, E. Coli -​ Domain: Archaea -​ Kingdom: Archaebacteria -​ Cell Type: Prokaryotic -​ Cell Structure: -​ Cell wall does not contain peptidoglycans -​ Cell membranes contain unusual lipids not found in any other organisms -​ “Ancient” organisms -​ Very primitive, live in extreme environments  -​ Cell Organization: Unicellular -​ Food Getting: Autotrophs (Make their own food) and Heterotrophs (Cannot make their own food) -​ Examples: -​ Methanogens, thermophiles and halophiles -​ Domain: Eukarya -​ Kingdom: Protista -​ Cell Type: Eukaryotic -​ Cell Structure: -​ Organisms that are neither plant, animal or fungi -​ Cell walls made of cellulose in some organisms -​ Some have chloroplasts -​ Cell Organization: -​ Most are unicellular -​ Some are colonial -​ Some are multicellular -​ Food Getting -​ Autotrophs + Heterotrophs -​ Examples -​ Amoeba, paramecium, algae, slime molds, giant kelp -​ Notes: -​ “Left over” group -​ Kingdom: Fungi -​ Cell Type: Eukaryortic -​ Cell Structures: -​ Cell walls are made of chitin -​ No chloroplasts -​ Cell Organization: -​ Most are multicellular -​ Some are unicellular -​ Food Getting: Heterotrophs (Cannot make their own food) -​ Examples: -​ Mushrooms -​ Yeasts -​ Puffballs -​ Molds -​ Mildew -​ Smut -​ Rust  -​ Kingdom: Plantae -​ Cell type: Eukaryotic -​ Cell Structure: -​ Made of cellulose -​ Chloroplasts are present -​ Cell Organization: Multicellular -​ Food Getting: Autotrophs (can make their own food) -​ Examples: -​ Mosses -​ Ferns -​ Liverworts -​ Cone-bearing plants -​ Flowering plants​ -​ Kingdom: Animalia -​ Cell Type: Eukaryotic -​ Cell Structure: -​ No cell wall -​ No chloroplasts -​ Cell Organization: Multicellular -​ Food Getting: Heterotrophs (cannot make their own food) -​ Examples: -​ Sponges -​ Worms -​ Mollusks -​ Arthropods -​ Fish -​ Amphibians -​ Reptiles -​ Birds -​ Mammals Barriers between species -​ Physical characteristics -​ Mating is impossible under natural conditions for many organisms -​ Not of the same species -​ Example: -​ Elephant and mouse -​ Mating occurs, offspring do not survive -​ Bullfrog eggs may be fertilized by the sperm of the leopard frog -​ Eggs develop to a point, but don’t survive  -​ Due to a drastic difference in the chromosomes​ -​ The offspring may survive, but they are not fertile -​ Example: -​ Horse + Donkey = mule -​ Mule is sterile, and won't be able to reproduce​ -​ Geographical Barriers -​ Many organisms simply don’t come into contact with each other -​ Example: -​ Grizzly bear and Polar Bear -​ Behavioral barriers -​ Many organisms, especially in the animal kingdom, won’t mate unless certain behaviors are shown -​ Example -​ Birds calling/singing Diversity of Living Things (Lesson 4 - Viruses) 7 Characteristics of life -​ MRS GREN -​ M. -​ Movement -​ Move using energy consumed by the organism -​ R. -​ Respiration -​ Release energy from food for cellular processes -​ S. -​ Sensitivity -​ Sense and respond to stimuli in the environment -​ G. -​ Growth -​ Living organisms use food to grow in size, or number of cells -​ R. -​ Reproduction -​ Produce offspring -​ E. -​ Excretion -​ Release waste products from cell processes​  -​ N. -​ Nutrition -​ Take in material for growth​ Classifying Viruses -​ Viruses are particles only able to reproduce by way of host cells -​ Originally comes from latin, meaning poison or toxin -​ Cell vs. Virus -​ Cell -​ Eukaryote or Prokaryote -​ Much more complex -​ Virus -​ Consists of a capsid, protein molecules, and DNA or RNA genetic code -​ Much less complex​ -​ Viruses are not alive -​ Classified as non-living particles because they cannot perform any of the processes that are the required characteristics of life -​ One characteristic they do share with living organisms: -​ Contain genetic material (DNA, RNA) that can be passed on -​ However, they require a host cell to reproduce​ -​ Basic Structure -​ All viruses contain nucleic acid (DNA or RNA) in the core, which is surrounded by capsid (protein coat) and an outer shell -​ Some viruses have lipid membranes around a capsid (e.g. HIV) -​ Shape can vary​ -​ Size of Viruses -​ Viruses are less than 0.1 micrometers in diameter -​ 5000 flu viruses fit into the head of a pin -​ Shapes -​ Helical -​ Helix shaped cell -​ Tobacco mosaic virus, Ebola​ -​ Polyhedral -​ Diamond shaped -​ Adenoviruses  -​ Pink eye -​ Common Cold -​ Pneumonia​ -​ Spherical -​ Sphere shaped -​ Coronavirus, Influenza​ -​ Complex virus -​ Robot shaped -​ Bacteriophages -​ Only infect bacteria -​ Bacteriophages -​ Viruses that invade and destroy bacteria cells -​ Have unique shapes and distinct head and tail regions -​ Robot shaped -​ Most abundant biological agent on earth -​ Many of them​ -​ Origin of viruses -​ Several theories -​ 1. Parasitic living organism that lost its ability to reproduce outside of another living cell -​ 2. Produced from fragments of genetic material of an already living organism -​ 3. Virus-like particles existed before the first cells (more ancient than any cell)​ Viral Replication and Transmission -​ Lytic vs. Lysogenic cycles -​ Two different ways viruses can replicate in a host cell -​ In the lytic cycle, the virus hijacks the host cell -​ Uses it to reproduce the virus -​ Host cell is destroyed in the process -​ In the lysogenic cycle, the virus incorporates its genetic material into the host cell’s genome -​ Infects it from within -​ Host cell remains intact -​ Virus remains dormant​  -​ The Lytic Cycle -​ 4 steps -​ Attachment to host cell -​ Synthesis of new virus -​ Assembly of new virus -​ Release of virus, destroying the host cell -​ ASAR -​ Can take as few as 25 minutes to produce as many as 300 new viruses -​ Viruses are release and can go infect new host cells -​ Examples: -​ Common Cold -​ Ebola -​ SARS-CoV-2​ -​ The Lysogenic Cycle -​ Host cell is not initially destroyed -​ Viral DNA can remain in dormant state for years -​ Called lysogeny -​ Host continues to divide with viral DNA inserted into its own -​ When triggered, viral DNA becomes active -​ Virus then enters the lytic cycle -​ Examples: -​ Herpes virus (cold sores) -​ HPV (genital warts) ​ Genetics Notes Lesson 1: Genetic Material + DNA -​ The Basics -​ A trait is a characteristic of an organism inherited (passed on from parents) or can be shaped by our environment (Ex: dyed hair color) -​ Heredity is the passing of information from one generation to the next -​ Genetic information is passed on using deoxyribonucleic acid, DNA, a molecule stored in chromosomes in the nucleus of every cell -​ DNA is organized into genes, units of information that carry code of a specific protein. These proteins make a visible trait or function. -​ Genetics -​ Study of genes, heredity and genetic variation in organisms -​ Fundamental molecule is deoxyribonucleic acid (DNA)​ -​ DNA -​ Proteins are assembled piece-by-piece to exact specifications -​ Enormous amount of information required; complex system -​ Details specific structure of the proteins inside our bodies -​ Stored in nucleic acids (set of molecules) -​ DNA is a nucleic acid, exists as a mass of long fibers called chromatin -​ Chromatin condensed into a chromosome -​ Chromosome: Package of DNA that is 3 meters long when stretched out, wrapping around proteins called histones -​ -​ Human cells contain 46 chromosomes, 23 from the egg, 23 from the sperm -​ A complete set of chromosomes is shown in a karyotype -​ Carp have 104 chromosomes. An onion has 6. They are always an even number, as they represent a set -​ -​ Repeating Nitrogenous Bases -​ DNA is a molecule that holds a code -​ The traits of an organism are determined by the order of 4 different molecules called nitrogenous bases (A. T, C, G) -​ Adenine -​ Thymine -​ Guanine -​ Cytosine -​ A pairs with T -​ C pairs with G -​ Structure of DNA -​ Building block/subunit of DNA is the nucleotide, made of 3 components: -​ Sugar -​ Phosphate group -​ Nitrogenous base -​ Nucleic acids are very large molecules that have two main parts -​ The Backbone -​ Made of alternating sugar and phosphate molecules bonded in a long chain -​ Each of the sugar groups in the backbone is attached to a third molecule called the nitrogenous base -​ ​  -​ DNA gets its name from the sugar molecule in its backbone (deoxyribose) -​ Four different nucleotides occur in DNA: -​ adenine (A) -​ cytosine (C) -​ guanine (G) -​ thymine (T) -​ Nucleotide basses of the DNA molecule form complementary pairs -​ Complementary pairing occurs due to hydrogen bonds -​ Adenine always forms 2 hydrogen bonds with thymine -​ Cytosine always forms 3 hydrogen bonds with guanine -​ The double stranded system is found in a helical shape called the double helix -​ The letters (bases) form words (codons) that in turn create sentences (genes) that code for different amino acids. -​ Proteins are chains of amino acids that preform a specialized function. The human genome contains over 25,000 genes. -​ -​ Chromosomes -​ Made up of DNA and packaging proteins to keep it organized -​ Most of the time, it’s in the form of chromatin (long unwound strands) -​ In eukaryotic cells, chromosomes are in the X-shape during cell division​ -​ Genes and Loci -​ The order of the nitrogenous bases is a code -​ The code is a read in sections called genes, by equipment in the cell -​ Each gene codes for a protein (i.e. traits of the organism) -​ The location of a gene in the chromosome is called the locus -​ Plural: Loci -​ The Genetic Sequence -​ The equipment of the cell reads genes and translates it into specific proteins -​ DNA → RNA → Proteins -​ DNA gets transcribed into RNA, which codes for proteins -​ The proteins are responsible for traits in the organism (e.g. eye colour, height, location of the limbs, hormones, heart tissue, etc.)  -​ The Human Genome -​ Consists of 3 billion base pairs -​ Actually 6 billion base pairs, as you have two copies of each chromosome -​ Approximately 25,00 genes that code for proteins ​ Lesson 2: Genetic Processes -​ Key Concepts -​ During Interphase, the cell lives, grown and replicates its DNA. -​ In the mitotic phase, the chromosomes distribute to daughter cells -​ A duplicated chromosome consists of two sister chromatids​ -​ Cell Division -​ Terminology -​ Parent cell: -​ DNA Replication: -​ 2 Daughter cells -​ The Cell Cycle -​ The cell cycle is a series of events that happen, and serve two main purposes -​ 1. To create daughter cells -​ 2. To allow growth and maturation of the daughter cells until cell division occurs again -​ Several phases designated by a letter that stands for what happens during the phase​ ​ ​ -​ S Phase -​ Synthesis of DNA -​ DNA is replicated in anticipation of division -​ Hereditary material (DNA) makes an exact copy of itself → during cell division each duplicate will move to a new cell -​ Creates identical daughter cells​ -​ G1 phase -​ G stands for Growth, or Gap -​ Primary growth and maturation of new cells right after cell division -​ Cell gets bigger -​ G2 phase -​ G stand for Growth, or Gap  -​ Secondary growth and maturation following DNA replication -​ Organelles and proteins necessary for cell division are produced -​ M phase -​ “M” for mitosis -​ Mitosis and Cytokenesis occur -​ Creates 2 daughter cells from a single parent -​ Take up a small fraction of the cell cycle -​ Most of the time is spent in G1, S, and G2 (Interphase) -​ Takes up 90% of the time -​ 10% is miotic events​ -​ Apoptosis + Cancer -​ All somatic cells have the same life cycle of growth and maturation -​ At some point in the cell’s life its programmed to slow and cease division -​ This programming determines the life of a group of cells -​ “Life” of a red blood cell is 120 days -​ Different cells have different life cycles -​ Programmed cell death is called apoptosis -​ Cancer cells divide ceaselessly, forming a mass called a tumor -​ -​ Function of Mitosis -​ Ensures genetic continuity by facilitating the division of DNA material, and its separation into two identical daughter cells -​ Each daughter cell has the exact same function(s) as the parent cell -​ Cells can be replaced without losing the overall function of a tissue -​ Allows for tissue repair and maintenance to occur without disrupting the organ -​ The Phases of Mitosis -​ Human somatic cells undergo mitosis in 0.5 - 1.5 hours -​ Mitosis is often a short process on some organisms, the phases (PMAT) can take as little as 30 minutes -​ In each phase, there are a number of events that occur -​ Prophase -​ Chromosomes become visible -​ Nucleolus disappears -​ Mitotic spindle forms -​ Nuclear envelope 1disappears -​ Metaphase -​ Chromosomes are arranged on the metaphase plate (middle of the chromosome) -​ Spindle fibers attach to the chromosomes  -​ Anaphase -​ Sister chromatids separate -​ Daughter chromosomes move to opposite ends of the cel -​ Telophase -​ Chromosome sets assemble at opposite poles -​ Nuclear envelope reforms around each set -​ Cytokenesis (division of the cytoplasm) follows -​ Cytokinesis -​ Process where the cytoplasm is divided in two -​ Cleavage furrow forms and the cell membrane pinches off the cytoplasm into two halves. Forms two cells. -​ Chromosomes and Chromatids -​ All genetic material must be copied prior to cell division -​ An exact copy of each cell’s DNA is made via DNA replication -​ Two identical copies of the same chromosome, known as sister chromatid, are joined together at the centromere. -​ The number of chromosomes = the number of centromeres -​ Before S phase -​ 1 chromosome in parent cell -​ 1 chromatid per chromosome -​ After S phase -​ 1 chromosome in parent cell -​ 2 chromatid per chromosome -​ After Mitosis -​ 1 chromosome in daughter cells -​ 1 chromatid per chromosome -​ As DNA replicates, a small amount of DNA is lost at its ends -​ To make sure that no important information is lost, telomeres form protective caps of unnecessary DNA sequences -​ Forms at the end of chromosomes -​ Errors in mitosis -​ A mutation is a change in the genetic material (DNA) -​ Mutations are important because they may have negative or positive effects on on the organism/offspring -​ Also important for studying inheritance of particular genes, and how the genes are altered -​ Mutations are a major source of genetic variation -​ Lead to changed in the structure of the DNA -​ May have evolutionary consequences -​ Variety of different types of mutations that occur -​ Due to errors in DNA replication and division of chromosomes -​ Spontaneous mutations occur as a result of of natural processes in the cell  -​ Mistakes in DNA replication happen quite often -​ Many of these mistakes are corrected during replication, as chemicals in the nucleus “proofread” newly replicated chromosomes -​ Induced mutations occur due to outside factors - a mutagen -​ Mutagen is natural or man-made chemical that can alter the structure and/or the sequencing of DNA -​ Most mutagens are harmful -​ Example: Poisonous mustard gas -​ Used in both world wars -​ Caused mutations in nerve cells that led to interference with the function of the cells -​ Other chemical mutagens have been found in cigarettes, and linked to lung cancer (transformation of lung cells) Lesson 3: Meiosis -​ Types of cell reproduction -​ Asexual reproduction -​ Involves a single cell dividing to make 2 identical daughter cells -​ Example: -​ A biological parent produces offspring genetically identical to them -​ Fragmentation -​ Mitosis + Binary fission -​ Sexual reproduction -​ Involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells -​ Examples: -​ Two biological parents produce offspring that are genetically unique -​ Meiosis is an example of sexual reproduction -​ Diploid cells (2n) -​ Have two copies of each chromosome -​ Zygotes, embryos and somatic cells(skin cells, neurons, muscle cells) -​ Haploid cells (n) -​ Have one copy of each chromosome -​ Gametes (sperm, eggs, spores) -​ Meiosis -​ Form of cell division that results in 4 cells, each contain half the number of chromosomes than the parent cell -​ Required for sexual reproduction to occur (combining of genetic material) -​ In many animals, like humans, meiosis occurs in the sex organs (ovaries and testes) -​ Karyotype  -​ The collection of all an individuals chromosomes, typically 46 -​ Some people may have more or less; results in a variety of outcomes -​ Homologous Pairs -​ While information on each homologous chromosome is very similar, they aren’t identical -​ They contain the same genes, but the information in those genes sometimes differ slightly (trains inherited from each parent are different) -​ An allele is a version of a gene -​ Meisos is the fundamental basis of sexual reproduction -​ Produces egg and sperm cells (gametes / germ cells) -​ Two haploid (n) gametes are brought together through fertilization to form a diploid (2n) zygote -​ Haploid sperm + haploid egg = Diploid zygote -​ Preparing of Meiosis -​ Before beginning meiosis, the cell must complete interphase (just like mitosis) -​ The cell grows during G1, replicates DNA in S, and grows and prepares for cell division in G2 -​ Now the cell has 46 chromosomes, and 92 chromatids (2x the number during G1)​ -​ Replication is the process of duplicating a chromosome -​ Occurs before division -​ Replicated copies are called sister chromatids -​ Held together at centromere -​ Meiosis forms haploid gametes -​ Meiosis must reduce the number of chromosomes by half -​ Fertilization then restores it to a diploid (2n)​ ​ ​ -​ Meiosis: Two part cell division -​ -​ Diploid → Homologous chromosomes separate → Sister chromatids separate -​ Homolog (Homologous chromosome): pairs of chromosomes in a diploid organism that have similar genes, although not necessarily identical -​ Meiosis overview -​ Two stages of cellular replication -​ Begins with one cell, then two, ends with 4 -​ The first cell which will undergo meiosis is called the parent cell (diploid, 2n) -​ The cells that are produced are called gametes (haploid, n) ​ -​ Haploid cell vs. Diploid -​ Haploid (n) -​ One copy of each chromosome -​ Non-homologous chromosomes -​ Diploid -​ Two copies of each chromosome -​ Three pairs of homologous chromosomes -​ Maternal and paternal origin -​ Prophase 1 -​ Chromosomes condense and nuclear envelope breaks down -​ In mitosis the chromosomes begin to arrange in one single file line down the middle of the cell -​ In meiosis, a pair of homologous chromosomes undergo synapsis (they line up beside each other and hug) -​ Homologous chromosomes pair up and exchange fragments (crossing over)  -​ Reason for genetic diversity between parent and offspring -​ Forms a tetrad (4 chromatid aligned) -​ Early prophase: -​ Homologs pair -​ Crossing over occurs -​ Late prophase -​ Chromosomes condense -​ Spindle forms -​ Nuclear envelope fragments -​ Crossing over: -​ Occurs during synapsis, when sections of DNA are exchanged between homologous pairs -​ Random events, produces more genetic diversity -​ Up to 25 crossovers per homologous pair -​ Homologous pairs join to form a tetrad -​ Summary: -​ Homologous chromosomes in a tetrad cross over each other -​ Pieces of chromosomes or genes are exchanged -​ Produces Genetic recombination in the offspring (non-identical) -​ Crossing over multiplies the already huge number of different gamete types -​ Metaphase 1 -​ Tetrads align in the midline of the cell -​ Called the metaphase plate -​ Each chromosome of the homologous pair are oriented to opposite poles -​ Sister chromatids stay together -​ In mitosis, the chromosomes are split into sister chromatids, which move to opposite poles -​ Anaphase 1 -​ Chromosomes move to the opposite poles -​ Spindle fibers pull the chromosomes to each pole -​ Unlike in mitosis, the sister chromatids remain together, pairs are separated -​ Telophase 1 and Cytokinesis -​ Homologous chromosomes continue moving to the poles -​ Each pole becomes a haploid (23 chromosomes, 46 chromatid) -​ Cytokenesis occurs as meiosis 1 finishes -​ Genetic material does not replicate again -​ Nuclear membrane/envelope reassembles -​ Spindle disappears -​ Newly formed cells are haploids (n=2)  -​ Each chromosome has two (non-identical) sister chromatid -​ Prophase 2 -​ Starting cells are haploid cells -​ Don’t have homologous pairs of chromosomes, only one copy of each -​ No interphase between Meiosis 1 and Meiosis 2, chromosomes are not replicated before prophase 2 -​ Chromosomes condense, nuclear envelope fragments, spindle fibers form -​ Chromosomes begin to move to the metaphase plate (middle line) -​ Metaphase 2 -​ Chromosomes line up single file at the cells center (forms the metaphase plate) -​ In metaphase 1, the homologous pairs line up beside each other -​ Anaphase 2 -​ Sister chromatid of each chromosome separate, begin to move to opposite poles -​ Sister chromatids separate from one another, now known as daughter chromosomes -​ Two cell poles also move further apart. Each pole contains a complete set of chromosomes -​ Telophase 2 and Cytokinesis -​ A nucleus begins to form in each pole (Nuclear membrane starts to form) -​ Spindle dissapears -​ Cytokinesis also occurs -​ Four daughter cells have been produced. -​ All of the daughter cells have half the number of chromosomes then the original parent (46 → 23) -​ Results of Meiosis -​ Gametes (egg and sperm) form -​ Four haploid cells (n) with one copy of each chromosome -​ One allele (variant) of each gene -​ Different combinations of alleles for different genes along the chromosome -​ Summary -​ Preceded by interphase which included chromosome replication -​ Two meiotic division, Meiosis 1 and Meiosis 2 -​ Called reduction - division -​ Original (parent) cell is diploid (2n) -​ Four daughter cells produced that are monoploid/haploid (1n) -​ Contain half the number of chromosomes than the original cell -​ Occurs in the testes for males (Spermatogenesis) -​ Occurs in the ovaries in females (Oogenesis) -​ Starts with 46 double stranded chromosomes (2n) -​ After 1 division - 23 double stranded chromosomes -​ After 2nd division - 23 single stranded chromosomes Lesson 4: Gametogenesis + Nondisjunction -​ Gametogenesis -​ Formation of gametes (through meiosis) -​ Male → Spermatogenesis -​ 46 -​ 23 -​ 23 -​ 23 -​ 23 -​ 23 -​ 23 -​ Female → Oogenesis -​ 46 -​ 23 + polar body (not functional) -​ 23 + polar body (not functional) -​ Importance of Meiosis -​ Increases genetic diversity within populations through: -​ Crossing over (makes diverse chromosomes) -​ Independent assortment of chromosomes (each gamete gets a different combo of chromosomes from the biological grandparents) -​ Different chromosome combinations -​ Random fertilization (random sperm meets with a random mature egg) -​ Spermatogenesis -​ One parent diploid cell (46 chromosomes) produces four haploid sperm cells (23 chromosomes) -​ A mature sperm cell is called a spermatozoon -​ Sperm cells are relatively small (compared to eggs) -​ They are motile, as they have a flagellum and flatten head that lets them move forward -​ Occurs in the testes -​ Two divisions produce 4 spermatids -​ Mature into sperm (spermatozoon) -​ Males produce approx 250,000,000 sperm a day -​ At the end of meiosis, cytoplasm is lost from the head, and a flagellum develops for motility -​ Oogenesis -​ One parent diploid cell (46 chromosomes) produces one haploid cell (23 chromosomes) and 2 polar bodies -​ Through unequal cytokinesis, the ovum rakes more cytoplasm -​ Leads to smaller polar bodies, which can’t be fertilized -​ Polar bodies disintegrate -​ A mature egg is called an ovum -​ Oogenesis happens in the ovaries -​ Two divisions produce 2 or 3 polar bodies that die, and 1 egg  -​ Immature egg is called oocyte -​ Starting at puberty, one oocyte matures into an ovum (egg) every 28 days -​ Oogenesis Spermatogenesis Number 1 parent cell produces 1 ovum 1 parent cell produces 4 (egg cell). spermatozoon (sperm cells). Time Meiosis 1 completed during Meiosis occurs continuously gestation of fetus (before birth). after puberty. Meiosis 2 completed after egg fertilization. Size Relatively large, spherical shaped Relatively small, flattened head cell. with long flagellum. Motility Non-motile Motile Location Occurs in the ovaries. Occurs in the testes. Mitosis Meiosis Number of Divisions 1 2 Number of Daughter Cells 2 4 Genetically Identical? yes no Chromosome # Same as parent Half of parent Where? Somatic cells Germ cells When? Throughout life At sexual maturity Role Growth and repair Sexual reproduction -​ Nondisjunction -​ Occurs when: -​ Two homologous chromosomes move to the same pole during Meiosis 1  -​ Two sister chromatids don't separate and move to the same poles during Meiosis 2 -​ Produces gametes with 22 or 24 chromosomes, instead of 23 in each -​ -​ Meiosis is not immune to errors and variation in outcomes -​ Nondisjunction can occur in Anaphase 1, when two homologous chromosomes move to the same pole -​ Can also occur during Anaphase 2, if the sister chromatids fail to separate from each other. -​ In both cases, this results in gametes with either an extra chromosome or missing a chromosome -​ Aneuploidy -​ An abnormal number of chromosomes -​ Monosomy: only one chromosome instead of a homologous pair -​ Condition which an individual only has one homologue -​ Trisomy: three homologous chromosomes instead of a pair -​ Most common type of polysomy -​ The zygote (new cell formed by sperm + egg) has an extra chromosome -​ Depending on the chromosome, will result in a variety of conditions -​ Polysomy -​ Condition where an individual has three or more of a specific chromosome -​ Examples of Trisomy -​ Down Syndrome -​ Trisomy 21 -​ Most common type of trisomy  -​ Result of meiotic nondisjunction in the female parent, and associated with the increased age of the maternal side -​ In Canada, 1 in 750 people are born with an extra Chromosome 21 -​ People with Down Syndrome inherit the physical appearance of their biological parents -​ Also have a characteristic facial appearance, and shorter stature -​ Mild to moderate intellectual disability -​ Klinefelter Syndrome -​ Trisomy 23 (47, XXY) -​ Condition is a result of the sex chromosomes -​ Receive an extra X chromosome from a biological parent -​ Occurs in 1/500 to 1/1000 births -​ People born with it have male sex characteristics -​ Results in lower production of testosterone, and higher production of estrogen during fetal development and puberty -​ May not produce as much body hair, may have some breast development, and may produce little to no sperm -​ Most people identify as men, and may choose to take testosterone -​ Triple X Syndrome (47, XXX) -​ Trisomy 23 (47, XXX) -​ Only in female sex -​ Condition is a result of an extra X chromosome from a biological parent -​ Occurs in 1/1000 births -​ People with Triple X Syndrome often experience no symptoms, or very mild symptoms -​ Some may experience some intellectual or learning disabilities -​ A very small percentage experience seizures and/or kidney disorders -​ Most identify as a women -​ Turner Syndrome -​ Monosomy 23 (45, XO) -​ Condition is a result of a monosomy of the sex chromosomes -​ Occurs in approx 1/2000 births -​ Characteristic may include short stature, improperly developed ovaries, webbed neck, thyroid conditions and heart defects -​ Chromosomal Structural Rearrangments -​ Structural rearrangements in chromosomes include partial duplications, deletions, inversions, and translocations (genes get moved) -​ Tend to occur during prophase 1 when homologous pairs align (during crossing over) -​ Duplications and deletions often produce offspring that survive and exhibit atypical physical and mental outcomes -​ 46, XY, t(9;22)​  -​ 46 chromosomes, XY sex -​ Part of chromosome 9 gets translocated to chromosome 22 -​ Diagnosing Nondisjunction -​ Prenatal Testing eFTS -​ In the first trimester, the Enhanced First trimester Screening test (eFTS) is preformed -​ eFTS is an ultrasound and blood work that looks for markers that increase the possibility of Down syndrome (trisomy 21) and Edwards syndrome (trisomy 18) -​ Prenatal Testing: NIPT -​ In the first trimester of pregnancy, a blood test can be done called Noninvasive Prenatal Testing (NIPT) -​ Looks for genetic “markers” in fetal DNA that is circulating in the pregnant persons blood -​ More accurate then eFTS -​ Only covered by OHIP for people that meet specific criteria (positive eFTS, etc.,) -​ Costs $500 for most -​ Prenatal Testing: Amniocentesis -​ After a positive eFTS and/or NIPT, amniocentesis is available at the beginning of the second trimester -​ Higher risk test, draws fetal cells from the amniotic sac (increased chance of infection) -​ Test can provide definitive diagnosis -​ Genetics and Inviability -​ Errors in genetic replication, or during meiosis or early mitosis in embryos can result in inviability (miscarriage) -​ 1 in 4 pregnancies end in a miscarriage -​ Errors in genetic replication are the most common cause of miscarriage ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Lesson 5: Mendelian Genetics -​ Long ago, people thought an organism's traits were determined in the way that paint colour mix -​ If you cross two different plants, offspring will be a combination of the 2 -​ Known as: Blending Model -​ Incorrect, and oversimplified -​ Heredity -​ Passing of traits from parent to offspring -​ Example: -​ Brother might have blue eyes, but parents have brown eyes -​ Mendels experiments -​ During the 1800s, Mendel studies genetics through experiments with pea plants -​ Controlled which plants pollinated other plants -​ Sperm cells from the pollen land on the pistil of a flower -​ Sperm cells then fertelize the egg cells in the pistil -​ Self pollination -​ When pollen from one plant lands on the pistil of the same plant -​ Cross-pollination -​ Pollen from one plants lands on the pistil of a different plant -​ True breeding -​ When a true-breeding plant self pollinates, it ALWAYS produces offspring with traits the same as the parent -​ Example: -​ True-breeding pea with wrinkled seeds self pollinates, it produces plants with wrinkled seeds -​ Generation Crosses -​ First generation Crosses -​ When mendel crossed a white and purple plant together, all the offspring were purple -​ Called hybrids (f1 generation) -​ -​ Second Generation -​ When Mendel crossed two of the purple hybrid plants (F1), some off the offspring were white -​ Trait that disappeared in the first generation always appeared in the second (F2) -​ Conclusions: -​ Two factors control each inherited trait -​ When organisms reproduce, the sperm and egg contribute 1 factor for each trait -​ Hypothesized that all purple offspring had one genetic factor for purple flowers, and on for white flowers -​ Somehow, the genetic factor for white flowers was masked in F1 -​ Alleles -​ Different forms of a gene -​ Located in the same position of each pair of homologous chromosomes, but have a different code​ -​ Dominant and Recessive Traits -​ An allele that blocks another allele is called a dominant trait (shown in a capital letter) -​ A dominant trait is seen when offspring have either one or two dominant alleles (BB or Bb) -​ A recessive trait is only seen when two recessive alleles are present in the offspring (bb)​ -​ Law of Segregation -​ Each parent has two alleles for each gene, and passes one of those alleles at random to their offspring (50% chance)​ -​ Genotype -​ Describes the genetic makeup (combination fo alleles) of an individual -​ Homozygous Dominant, heterozygous, homozygous recessive -​ “The genes” -​ Phenotype -​ Describes how the genes are expressed in an individual (how they appear) -​ “The look” -​ Complete dominance -​ Form of inheritance where the dominant allele completely masks a recessive allele -​ Key Terms -​ Homozygous - Identical alleles -​ Heterozygous - two different alleles -​ Dominant - Allele that masks, or the expression of, and alternate allele; trait appears in the heterozygous condition -​ Recessive - Allele that is masked by a dominant allele; does not appear in heterozygous condition, only homozygous recessive -​ Genotype - Genetic makeup of an organism -​ Phenotype - Physical appearance of an organism (Genotype + environment) -​ Monohybrid Cross - Genetic cross involving a single pair of genes (one trait); parents differ by single trait (Aa x AA) -​ P = Parental generation -​ F1 = First filial generation; Offspring from a genetic cross -​ F2 = Second filial generation of a genetic cross  -​ Monohybrid Cross -​ Parents differ by a single trait -​ Crossing two pea plants with different stem sizes, one tall one short -​ T = allele for Tall -​ t = allele for dwarf -​ TT = Homozygous tall plant (dominant) -​ tt = homozygous dwarf plant (recessive) -​ T T x t t -​ Mendel’s principles -​ Principle of Dominance -​ If one allele masks another, that allele is dominant over the other. This was shown by the f1 heterozygotes all having the dominant phenotype -​ Principle of Segregation -​ A pair of alleles segregate from each other during meiosis cell division (gamete formation) so that only one allele will be present in each gamete. Lesson 6: Dihybrid crosses -​ Cross between two individuals with two different traits -​ Used for complete dominance patterns -​ Example: pea shape and pea colour -​ FOIL -​ Law of Independent Assortment -​ States that if genes are located on separate chromosomes, they will be inherited independently of one another -​ Four possible combinations of alleles that can be created through independent assortment -​ When combining 2 fully heterozygous individuals (TtPp x TtPp) the results will always be in the ratio of: -​ 9:3:3:1 Lesson 7: Beyond Mendel -​ Other types of inheritance that Mendel never considered (Nonmendelian Genetics) -​ Incomplete Dominance -​ Condominance -​ Multiple Alleles -​ Polygenic Traits -​ Sex-Linked -​ Incomplete Dominance -​ The hybrid (heterozygous) displays a third phenotype -​ Neither trait is completely dominant, as a result theres a blending phenotype -​ Red Flower x White Flower = Pink -​ (RR) x (WW) = (RW) -​ CrCr = homozygous Red -​ CrCw = heterozygous pink -​ CwCw = homozygous white  -​ Codominance -​ In this pattern, the heterozygous genotype expresses both alleles equally -​ Rather than blending or mixing, each trait is shown in the phenotype of the organism -​ There is no dominant or recessive trait -​ Black Cow x White Cow = Spotted Cow -​ BB x WW = BW -​ Expressed equally -​ Red phenotype x White phenotype = red and white spotted phenotype -​ RR x WW = RW -​ Blood ** Add in Lesson 8: Polygenic + Sex Linked traits -​ Polygenic traits -​ Poly = many -​ Genic = origin -​ Multiple origin traits -​ Eye colour, height and skin colour are examples -​ Traits produced by more thank one pair of genes, results in a variety of phenotypes -​ No punnett square possible -​ Sex Linked traits -​ Hemophilia is a sex linked recessive traits -​ Non-Mendelian -​ Still use dominant and recessive -​ Alleles are on the sex chromosomes (XX, XY) -​ All humans have at least one X chromosome -​ Traits tend to be on the X chromosome, as opposed to the Y chromosome -​ X chromosome is much larger, and contains more genes than the Y chromosome -​ X-linked traits -​ Hemophilia -​ Carried on the X chromosome -​ Recessive -​ Autosomes (autosomal) -​ Chromosomes 1-22 (excluding sex chromosomes) -​ Sex linked recessive traits are more common in XY genotypes than XX -​ XY only has one X chromosome (No backup) -​ XX has two X chromosomes (backup) -​ Sex linked dominant traits exist -​ Not all disorders that have a genetic component are based off of one gene, many involve different genes and autosomes -​ Sex chromosomes vary in different animal species Evolution -​ All living things share a common ancestor -​ We can draw a tree of life to show the relationships among organisms -​ Evolution is the process by which one species gives rise to another -​ Biological Diversity (Biodiversity) -​ Variety of living things on our planet -​ How did the millions of different organisms of many shapes and sizes come to live in so many different habitats on earth? -​ Why do these organisms live where they do? -​ How did the organisms arise?​ -​ Which organisms are related to one another? -​ What adaptations allow organisms to live in a specific environment? -​ How do organisms change over time? -​ Scientific Theory -​ a) an explanation that is based on observation, experimentation, and reasoning -​ b) It is supported by a lot of evidence -​ c) It doesn’t conflict with existing experimental results -​ Evolution: “Change over time” -​ Evolution is the process by which modern organisms have descended from ancient organisms -​ Heritable change in the characteristics within a population from one generation to the next -​ Evolutionary Theory: -​ Collection of scientific facts, observations and hypotheses that try to explain the diversity of life on earth -​ Law vs. Theory -​ Theory of Evolution -​ Provides an explanation on how species change over time -​ Suggests that modern species came to be as a result of changes to the heritable information (DNA) passed from one generation to the next. -​ Explains that all life on earth shares a common ancestor -​ Early ideas -​ Fixed / Immutable species -​ Species were considered to be special creations from god -​ Fixed or immutable (does not change) for all time -​ The earth is young  -​ People thought the earth was less than 10,000 years old -​ It was thought to be relatively unchanging -​ Transmutation -​ Around 1800, scientists began to wonder if species could transmute (change) -​ Lamarck thought that if an animal acquired a characteristic during its life it could pass it onto its offspring -​ Hence giraffes got their long necks through generations of straining to reach high branches -​ Evidence - Geology -​ Geologists such as Hutton and Lyell challenged the idea that the earth was young -​ Based on geologic observations -​ Studies Rock formations, erosion and sedimentation rates -​ Concluded it must have taken millions of years for rock formations to be made -​ Evidence supports the theory of uniformitarianism - earth was formed by slow moving processes which are still occurring today -​ Theories of Geology -​ Catastrophism -​ Volcanoes, floods, earthquakes -​ Examples of catastrophic events that are thought to be responsible for mass extinctions and formation of landforms -​ Gradualism -​ Canyons carved by rivers show gradual change -​ Idea that changes on earth were caused by small steps over a lot of time -​ Uniformitarianism -​ Rock strata show that geologic processes still happening today, add up over long periods of time to cause great change -​ Evidence for Evolution -​ Fossils and Strata -​ Geologist William Smith and Georges Cuvier were studying fossils and showed that different species existed in the past compared with today -​ Darwin's Voyage -​ Charles Darwin toured the world on the HMS Beagle (1831-36) -​ Dazzled by the amazing variety of life, and wondered how it originated​ -​ Darwin’s Theory of Evolution -​ Charles Darwin -​ Born in 1809 in England -​ Naturalist, geologist, biologist -​ Wrote On the Origin of Species -​ Incredibly influential -​ In 10 years it was accepted as fact in the scientific community -​ Naturalism and Imperialism -​ Darwin participated in colonial missions during imperialism -​ Naturalists did not wage violence on the communities they traveled to, instead they conducted surveying missions for the empires -​ Naturalists, geologists and ethnologists would accompany the expeditions -​ Expeditions would survey the land in colonies produce maps, collect information about cultures, and identify resources -​ Information was used as a tool for continued expansion -​ HMS Beagle -​ Darwin was invited to bethe crew naturalist on the Beagle -​ For the next 5 years, the beagle surveyed the coast of South america -​ Darwin explored the islands and continents, observing flora and fauna, and collecting species -​ Species Variability -​ On his trip Darwin noticed interesting things -​ Species varied immensely across the globe -​ Some areas had unique organisms not found anywhere else -​ Species living in similar habitats in different parts of the world looked and act very similarly -​ -​ Local species diversity -​ Darwin observed that there was significant species variety in local communities -​ Related animal species that lived in different habitats had different features -​ “Darwin’s Finches” -​ Darwin observed that finches on different islands in the Galapagos had very different beak shapes. ​  -​ Fossil Records -​ Darwin observed that species varied over time, based on fossils -​ He found the skull of a Megatharium on the Argentinian coast -​ Concluded that modern species evolved from ancient ancestors -​ Contemporary Influences -​ While on the Beagle, Darwin read Lyell’s book Principles of Geology -​ Darwin learned about the geological process that Lyell described, like gradualism -​ He found marine animal and shell fossils that were on land, and 12,000 feet above sea level -​ Due to gradual movements of the Earth’s crust over time Lesson 2 -​ Darwin's observations -​ On his travels, darwin discovered that an enormous number of species lived on earth -​ On one single day in a brazilian forest, Darwin collected 68 different species of beetles -​ Observed that many of the plants and animals were extremely well suited to the environment that the lived in -​ For example: -​ Adaptations seen in desert organisms were not seen in forest organisms -​ ADAPTATIONS: -​ Characteristics of organisms that enhance their chances of survival and reproduction in specific environments -​ Why do organisms exhibit certain adaptations? -​ Why is there such a variety of ways of reproducing? -​ Fossils -​ Fossil: Preserved remains of an ancient organism -​ Darwin collected fossils -​ Some fossils resemble organisms that were still alive -​ Others were unlike any creature he’d ever seen -​ Why have so many species become extinct? -​ How were the species seen in fossils related to living species? -​ Dawin became convinced organisms had changed over time -​ The Galapagos Islands -​ Small cluster of islands in south america  -​ Port of call was the most influential on Darwin’s developing theory -​ Islands were close together but had different climates -​ Lower islands → hot, dry and nearly barren -​ Higher islands → greater rainfall, rich vegetation -​ Organisms on each island had special adaptations that allowed them to survive only on that island -​ Adaptations for one island wouldn’t be helpful for another -​ Darwin became interested in the large land tortoises -​ Hood Island tortoise -​ Long neck -​ Curved shell that was open around the legs and head -​ Allows the tortoise to reach up high to eat the sparse vegetation -​ Isabela Island tortoise -​ Short neck -​ Dome shaped shell -​ Allows the tortoise to feed upon vegetation that grows close to the ground -​ Journey home -​ Darwin spent most of his time observing the collections of organisms he had -​ Began to wonder if the animals on different islands had once been members of the same species -​ Separate species evolved from ancestral species after becoming isolated from one another -​ Many people found Darwin’s ideas too shocking to accept -​ 1. Many people believed that the earth was only a few thousand years old. They believed that the earth and all organisms had only been created a few thousand years ago -​ 2. It was believed that since the creation of earth and its life forms, neither the planet nor its living species had undergone an changes -​ 3. Rocks and major geological feature were caused by catastrophic events that humans rarely witnessed -​ During Darwin’s time, scientist were studying features on earth in great detail -​ Began to study rock layers called strata -​ Data they collected suggested the earth was very old, and had changed slowly over time -​ Evidence showed that earth was millions of years old, and the processes that changed earth in the past are still present today -​ Georges Cuvier -​ Pioneer in paleontology (study of fossils) -​ Collected fossilized bones and spent years reconstructing what they looked like -​ Realized that fossilized animals were very different from any living species, and some had become extinct -​ Discovered the deeper and older strata contain fossils that are increasingly different from living species -​ The older the stratum → the more dissimilar the fossils to current life forms -​ Discovered many sudden changes in the kinds of fossils found in one stratum to the next -​ Hypothesis termed “Catastrophism” -​ Led to the acceptance of the ideas of geologic change and extinction -​ Catastrophism -​ Principle that events in the past occurred suddenly and were caused by different mechanisms than those operating today -​ Catastrophes in the past were responsible for destroying certain species -​ James Hutton -​ In 1795, published hypothesis about the geologic forces that shaped the earth -​ Proposed Gradualism -​ a) Layers of rock form very slowly -​ b) Some rocks are moved up by forces beneath Earths surface to form mountains -​ c) Mountains and valleys are shaped by natural forces, sich as rain, wind, and temperature -​ d) These processes occur slowly over millions of years -​ Charles Lyell -​ Idea was called uniformitarianism -​ Principle -​ Mechanisms of change are the same over time. Same geologic forces active in the past are still operating today -​ Darwin had a copy of Lyell’s book, which helped him understand the geological forces acting upon the earth -​ In order for life to change over time, the earth would have to be extremely old -​ Jean-Baptiste Lamarck -​ One of the first scientists to propose that living organisms had changed over time -​ Published his Hypothesis: Theory of Acquired Characteristics  -​ Individuals acquire traits during their lifetime as a result of their experience of behaviour, then pass these traits onto their offspring -​ If you gain big muscles → your children will have big muscles -​ If you lose a finger → your children will be missing a finger -​ His theory was quickly rejected, but it was still important -​ Lamarck was the first to recognize that organisms change over time -​ First to develop a hypothesis about evolution -​ Among the first to propose that organisms are adapted to their environment -​ Thomas Malthus -​ Published a book about his thoughts and ideas on human population growth -​ Had an impact on Darwin’s developing theories -​ Noted that human babies were being born faster than people were dying -​ Stated that if the human population kept growing at a rapid rate, eventually there wouldn't be enough space or resources to support the population -​ Darwin realized that this applied strongly to plants and animals -​ Darwin knew that a plant would produce thousands of seeds -​ Only a small portion of the seeds would germinate and grown into a new plant -​ Only a small amount of these would successfully reproduce -​ What factors determine which offspring survive and reproduce, and which will not? -​ Key question is the foundation of Darwin’s theory of evolution -​ Developing his Theory of Evolution -​ Darwin arrived back in England in 1836 -​ Began to study the fossils and specimen collected -​ Filled notebooks with his ideas about the diversity of life and how it evolved over time -​ Didn’t publish his book till 1859 -​ Darwin noticed many examples of adaptations -​ Explained that organisms become “adapted” via natural selection -​ Natural selection -​ Process in which individuals with certain inherited traits leave more offspring than individuals with other traits -​ Darwin was reluctant to publish his ideas -​ Challenged fundamental scientific and religious beliefs -​ Continued his studies  -​ Instructed his wife to publish them when he died -​ In 1858 Darwin received a letter from Alfred Russel Wallace -​ Wallace summarized his thoughts on evolutionary change -​ Wallace arrived at the same conclusions as Darwin -​ Darwin quickly published his findings, after 18 months -​ In 1859, Darwin published his book “On the origin of species by Means of natural selection” -​ Darwin proposed a mechanism for evolution that he called natural selection -​ Presented evidence that evolution had been been happening for millions of years -​ Continues in organisms alive today -​ Causes some uproar: some felt it was brilliant, others were bitterly opposed -​ In his book, Darwin discusses descent with modification -​ All organisms descended from a common ancestor -​ Darwin's Finches -​ While in the Galapagos islands darwin observed 13 different species of finches -​ Each species has a beak adapted for a specific type of food -​ Darwin thought that all 13 came from a common ancestral finch -​ Over millions of years descendants of these ancestors had accumulated modifications, or adaptations that fit them to a specific environment -​ Descent with modification → Diversity of life on Earth today -​ Artificial selection -​ Darwin noted that plants and animal breeders were aware the variations existed in living organisms, and through selective breeding they could improve their crops and livestock -​ Selective breeding -​ Method of breeding where only the organisms with desirable traits are chosen to produce the next generation -​ Humans select the variations they find to be the most useful -​ Evolution by Natural Selection -​ Concept One -​ Organisms beget like organisms -​ The offspring of an organism will resemble their parents -​ There is stability in the process of evolution -​ Concept 2 -​ In any population, there are variations among individuals  -​ Some of these variations are passed to future offspring -​ Concept 3 -​ The struggle for existence -​ Members of a species compete for food, water, living space and other resources -​ Competition and favorable characteristics determine which organisms live and reproduce -​ Concept 4 -​ The number of individuals that survive and reproduce in each generation is small compared to the number produced -​ Concept 5 -​ Which individuals survive and reproduce and which won’t is determined by how well suited they are to their environment. -​ Darwin called the ability of an individual to survive and reproduce “fitness” -​ Concept 6 -​ Fitness is the result of adaptations -​ Concept 7 -​ Individuals with characteristics that aren’t well suited to their environment either die or leave few offspring -​ Concept 8 -​ Survival of the Fittest -​ Individuals that are best suited to their environment survive and reproduce, passing on favorable traits to future offspring -​ Common Descent → all things are derived from common ancestors -​ Descent with Modification -​ Descendants of the earliest organisms spread into different habitats over millions of years -​ They accumulated various adaptations -​ Evolution replaced the phrase “descent with modification” -​ Natural selection -​ struggle for existence -​ natural variations among members of a species -​ environment’s role in evolution -​ Species evolve, individuals do not Lesson 3 -​ Natural selection -​ Survival of the fittest -​ The few organisms that survive in each generation have the traits best suited to their environment -​ The survivors then reproduce, passing the advantageous traits onto their offspring -​ The organisms that don’t survive don’t pass the disadvantageous traits on -​ Each new generation has a higher population of individuals with the advantageous traits -​ Survival of the Adaptive -​ Fitness = an individual's ability to survive and reproduce in it’s specific environment -​ Certain adaptations make individuals better suited to their environment -​ Individuals with the adaptations increase their fitness, and pass their traits on -​ Natural selection doesn’t make organisms better -​ Organisms that are able to adapt and respond to changes are most likely to survive -​ The adaptations allow an organisms to pass on their genes -​ 1) Individuals do not evolve, a population does -​ 2)Natural selection can amplify or diminish inheritable traits -​ 3)Environmental factors vary from place to place over time. A trait that’s favored in one environment may be useless, or harmful, in another -​ Evidence for Evolution -​ Fossil Record -​ Fossils provide the most evidence of evolution -​ Fossils are a record of the history of life on earth -​ Many fossils are of organisms that are no longer living -​ These fossils often resemble organisms living today -​ Shows that past organisms are different from present day organisms -​ Many species are now extinct -​ Strata -​ Scientists try to find the relative age and absolute age of a fossil -​ Relative age -​ Age of an object relative to other objects  -​ When scientists study strata, fossils found at the lower part are deemed older than those at higher strata -​ Absolute age -​ Actual age of the fossil in years -​ Radioactive dating processes are used -​ Fossils contain radioactive isotopes that have a half life -​ Age is determined by measuring the amount of particular radioactive isotopes it contains -​ Transitional fossils -​ Have features and characteristics that are between ancient ancestors and their descendants -​ In 1862 the skeleton of an Archaeopteryx was found -​ Had the features of both reptiles and birds -​ Believed that birds evolved from reptiles -​ Fossil was the “Missing link” -​ Fossils don't contain soft tissue; limitations to the info fossils can provide -​ Geographic distribution of living organisms (Biogeography) -​ Study of the locations of organisms around the world -​ Use of geography to describe the distribution of species -​ Darwin wondered why places geographically similar had different organisms -​ The organisms were behaviorally and anatomically similar -​ Darwin concluded species living on different continents had each descended from different ancestors -​ Dome organisms on each continent were living under similar conditions -​ they were exposed to similar pressures of natural selection -​ Led to different animals evolving with similar features -​ Divergent evolution -​ Process of 2+ related species becoming dissimilar through evolution -​ Elephant and Wooly mammoth -​ Convergent evolution -​ Unrelated species adapting to similar environments, leading to analogous structures -​ Comparative anatomy -​ Homologous body structures  -​ Species that share a common ancestor should have similar characteristics -​ Known as homology -​ Anatomy of humans (bipedal, upright) and gorillas (quadrupedal, hunched forward) -​ Homologous Structures: Body parts that are similar in structure, but can be different in function -​ Example: -​ Bone structure in the arm of a human, cat’s foreleg, horses foreleg, bat wing, and dolphin flipper -​ All contain a humerus, radius, ulna, carpals, metacarpals, phalanges -​ Same arrangement of bones, different functions -​ Each of the limbs has adapted to helps organisms survive in different environments -​ All these animals shared a common ancestor, as they have the same forelimb bone structure -​ Analogous structures -​ Similar functions, different structure -​ Wings of a bird and bat -​ Signify a more distant ancestral relationship -​ Look similar externally -​ Vestigial organs -​ “Left over” from a previous ancestor, serve no purpose -​ Show a relationship to organisms that lived in the past -​ Example: Appendix, tailbone, tonsils, wisdom teeth -​ Appendix -​ Darwin proposed it was used by ancestral apes to digest cellulose from leafy vegetation -​ Recent evidence suggests it used to store good gut bacteria, re-immunize the digestive system -​ It can become infected, once removed there's no clear impact on human health -​ Other mammals have an appendix -​ Hip and Leg bones in whales -​ Tailbones in humans  -​ Embryology -​ Study of embryos and their development -​ Many embryos of different species look very similar in early stages -​ Example -​ All vertebrate embryos have pharyngeal gill slits near their throat, and a postanal tail at some point -​ Although they look alike at early stages, the similarities fade as development continues -​ Proves that these organisms shared a common ancestor -​ Biological Molecules -​ Scientists observed similarities at a molecular level -​ All species of life have the same basic genetic machinery of DNA and RNA -​ All types of green plants have similar types of chlorophyll -​ Cytochrome C -​ Essential protein for cellular respiration in humans -​ Converting glucose into energy -​ In humans and chimps the structures of it are almost identical → relatedness between us -​ Spider monkeys and macaques do not have identical proteins → more recent common ancestor than humans and chimps -​ Hemoglobin -​ Protein within red blood cells that carries oxygen -​ Coden for in DNA -​ Found in all vertebrates → all share a common ancestor -​ By comparing differences we can make an evolutionary tree -​ LUCA -​ All life uses the same genetic code to produce proteins -​ Provides evidence of one common ancestral cell for all life -​ “Last Universal Common Ancestor” -​ Estimated to have lived over 3.5 Billion years ago -​ When the earth was 560 million years old -​ Was anaerobic -​ Doesn’t require oxygen -​ Dependant on H2 and CO2 -​ Likely that it was a thermophile Systems Lesson 1 -​ Nutrition and digestion -​ All living things need essential nutrients to survive -​ Basic chemical building blocks -​ Six Essential nutrients -​ Macronutrients -​ Carbohydrates -​ Proteins -​ Fats -​ Water -​ Micronutrients -​ Vitamins -​ Minerals -​ Molecules found in food are too large and complex for cells to use them -​ Digestive system breaks the food into smaller molecules, used for energy -​ Macromolecules build and maintain cell structure and function -​ Carbohydrates -​ Composed of carbon, hydrogen, and oxygen atoms -​ Source of energy accessed very quickly -​ Carbs can be simple molecules, such as glucose, or more complex, such as starch -​ Simple Sugars are found in fruits (fructose) and milk (galactose) -​ Examples of monosaccharides (mono = 1, sacchar = sugar) -​ Basic unit of carbs, can’t be broken down any further -​ Monosaccharides combine to form disaccharides and polysaccharides -​ Disaccharides are a double sugar -​ Form when two simple sugars combine -​ Ex: Sucrose (glucose-fructose), Lactose (Galactose-glucose), Maltose (glucose-glucose) -​ Polysaccharides are more complex, made of many simple sugars combined -​ Plants make starch, and animals make glycogen. -​ Both are made of glucose subunits -​ Cellulose is made by plants; provides structural support -​ In humans, glucose gets converted into glycogen -​ Broken down into glucose when energy is needed -​ Fiber is made of cellulose, and is found in fruits, veggies, whole-grain breads etc., -​ Known as “roughage”; not completely digested, cleans out the gut and moves food and waste through the digestive system -​ Lipids (fats) -​ Essential source of energy and provides building materials for cell membranes and hormones  -​ Insulate the body from the cold, protects organs from injury, absorbs vitamins and conducts nerve impulses -​ Made of a glycerol backbone, attached to three fatty acid tails -​ Sources include nuts, grains, seeds, meat, eggs, cheese etc., -​ Three types -​ Saturated fats -​ Straight chain bond -​ Mostly found in meats -​ Unsaturated fats -​ Cis Double bond between 2 carbons -​ “Good” fats, mostly found in plants -​ Trans fats -​ Hydrogenated Trans double bond between 2 carbons -​ Partially saturated - unsaturated fats, not healthy -​ Proteins -​ Made up of amino acids -​ Joined together by peptide bonds -​ Form polypeptides -​ Antibodies, enzymes and hormones are proteins -​ Help build and repair muscle and cell membranes -​ Our cells cant make 9 of the amino acids from other molecules, known as the “Essential amino acids” -​ Sources of essential amino acids include meat, legumes, eggs, cheese, milk, whole grain products -​ Vitamins and Minerals -​ Minerals are inorganic compounds that the body needs in small amounts -​ Enable certain chemical reactions and help build bones -​ Don’t contain carbon, absorbed into bloodstream -​ Essential components of hemoglobin, hormones, enzymes, vitamins -​ Come from the earth -​ Vitamins are required in the body in small amounts, but they are crucial -​ Found in plants and animals -​ Serve as coenzymes, needed to make enzymes function -​ Involved in tissue development and growth -​ Helps the body fight and resists disease -​ Body produces vitamin D when exposed to sunlight -​ Vitamin K and some B vitamins produced by bacteria in t