Biology 2 PDF

# Biology 2 ## Theories of evolution: ### Charles Darwin (& Wallace): * Species can change over time, new species come from pre-existing species. In any population, there exists variation traits. (change over many generations.) * Mechanism of how new species: Natural selection * e.g. giraffe:...

# Biology 2 ## Theories of evolution: ### Charles Darwin (& Wallace): * Species can change over time, new species come from pre-existing species. In any population, there exists variation traits. (change over many generations.) * Mechanism of how new species: Natural selection * e.g. giraffe: variation: longer necks, allowed to reach more food, therefore survived more, increased. ### Jean Baptiste de Lamarck * Doesn't consider populations to have variations. Changes offsprings. (Change over 1 generation) * Mechanism of how new species: Acquired inheritance. * e.g. Giraffe: parents stretching for food over life, so offspring would have longer necks. ### 5 Points Darwin/Wallace: 1. Members of species often different from each other 2. Always more offspring than parents 3. Size of population does not change 4. Some offspring do not survive (survival of fittest) 5. Offspring look like parents. ### Variation type | **Variation type** | **Definition** | **Sources of Variation in population** | |---|---|---| | Structural | Large changes in the DNA like big deletions or duplicating that affect how individuals look or behave | | | Behavioural | Differences in how individuals act or respond to their environment e.g. mating rituals or foraging habits | | | Biochemical | Variations in the chemical processes or substances within organisms like differences in enzyme levels or metabolic pathways | | | Developmental | Differences in how organisms grow and develop; affect size shape and function | | | Physiological | Differences in how organisms function internally, such as in heart rate or temperature regulation | | | Geographic | Differences in traits among populations that have been isolated in different geographic areas, due to environmental factors | | ### Natural selection: * Phases of how natural selection occurs * **Variation** (from mutations) genetic mutations cause new features to emerge * **Selection pressures** (in the environment provide) * **Struggle for survival** - only the fittest survive * **Reproduce** - only the fittest do - passing fit alleles or features to emerge * **Frequency** of these fit alleles increase in population. ### Artificial selection/selective breeding: * **Definition:** The selection of favorable traits by humans for human benefit. e.g. bigger cows for meat. * **Bad:** * Organisms less able to survive on own. * Health problems. * Decrease in genetic diversity. * **Good:** * Follows VSSRF still. * Genes still passed from parent to offspring. ### Selective breeding methods: * **Inbreeding:** Mating of closely related individuals, e.g. parents and siblings. * **Line breeding:** Mating of less closely related individuals e.g. cousin, aunts, uncles. * **Overall:** Picking an organism with favorable traits, breeding it with another similar, not breeding unfavourable traits. ### Gene pools and allele frequency * **Gene pool:** Genetic information present in a population of organisms. Expressed in terms of frequencies (proportions). * **Allele frequency:** Number of copies of an allele / total number of alleles in population. ### Calculating allele frequency: 1. Calculate total # of alleles in pop: Individuals X 2 2. Using possible genotype, work out the total number of each allele. 3. Calculate the allele frequency for the dominant and recessive alleles using formula 1. **Example:** Pop: 50. 20 homozygous dominant (TT), 11 heterozygous (Tt) 1. 50 x 2 = 100 2. TT = 20 ind. T = 40 Tt = 11 ind. T = 11, t = 11 tt = 19 ind. t = 38 3. T = 51/100 = 0.51 t = 49/100 = 0.49 ## Speciation, convergent and divergent evolution * **Gene flow:** Genes in population exchange through breeding, genes flow through generations. * **Interrupted due to isolation:** (2 groups) No exchange, different selection pressures, different characteristics selected for. Over time, incapable of interbreeding. ### Divergent evolution: * Or adaptive radiation, when one ancestral species changes over geological time. * *Examples:* Early primate: ape, lemur, species A, species B, species C, species D, species E. ### Convergent evolution: * Natural selection may act on distantly related species to produce superficial similarities, not due to shared ancestry, adopted in a similar niche. * *Examples:* Dolphin (mammal), Shark (fish) * **Divergent evolution structure name:** Homologous. * Def: Similar structure, adapted to different functions in different animals, e.g. pentadactyl limb. * **Convergent evolution structure name:** Analogous. * Def: Different structures inside different animals adapted for similar function e.g. bird, bat, butterfly. ## Evidence for evolution: Fossils * **Fossil:** The remains or traces of an organism that once existed. Skelebi structures/hard parts resist weathering most common fossil. * **Living fossil:** An existing species of ancient lineage remained unchanged in form for a long time. * **Transitional fossil:** Fossil that shows intermediate state between ancestral form and that of it's descendant. * **Relative dating:** Determines relative order fossils are buried. * **Absolute dating:** Uses the amount of radioaching remaining in surrounding rock to determine age. ### Description of Fossilization: 1. Death and Decay * Soft body parts decay, leaving only hard e.g. bones. 2. Deposition * Hard body parts rapidly buried by sediment e.g. silt and sand, accumulate over time, more layers. 3. Replacement * Hard body parts dissolved by water seeping through sediment and replaced by minerals, creating a rock repical of org shape. 4. Discovery * Weathering and erosion wear away rock to reveal fossil ## Evidence for evolution - Biogeography: * Biogeography - The study of how the continents move across the earth, and how this directly affects the location of organisms. * **Examples:** Finding marsupials in South America and Australia. * Marsupials evolved at a time where South America were connected as one land mass (likely Gondwana). There is a common ancestor of South America and Australian marsupials. Speciation occured to result in all the species existing today. They adapted to the specific conditions on the specific continents. ## Evidence for evolution: * When populations become new species, they retain some characteristics in common. These structures can be compared and their evolutionary relationship inferred. ### Comparative anatomy: * Anatomy: Study of bodily structure of living organisms. * **Vestigial structures:** Functionless structures found in organisms. Characteristics such as forelimbs, may be used for different purposes because the selection pressures for different species would be different. * **Example:** The pentadactyl limb in vertebrates. * The arrangement of the forelimbs have a similar pattern but the limbs serve different functions. * (Homologous structures provide evidence for divergent evolution) ### Comparative embryology: * Embryology: Study of how embryos develop. * Adult vertebrates have certain differences, many embryos demonstrate similarities during early stages of development. **Example:** Chicken + human embryos are similar but not when fully formed. * **Embryos show features that are not seen when fully developed (tails, gills, slits).** * As the embryo develops, goes through a variety of stages. Many of these stages show homologous structures with different species. * **Embryological similarities explained by inferring that these organisms all had common ancestry.** ### DNA and Phylogenetic trees * The basic structure of DNA and proteins is identical for all species. Small differences in the sequence of amino acids can be used to determine the evolutionary relationship between species. * The sequence in nucleotides in DNA also can be compared between species. Mutations cause small differences, that can accumulate over time. The more differences in DNA, the more distantly related the species are. * **Phylogenetic trees:** **recent common ancestor** *(Example)* Human, Chimpanzee, Gorilla, Orangutan **most closely related**