Test Guide Unit 4 Evolution & Biodiversity

Unit 4: Evolution & Biodiversity ❖ Microevolution = changes in one population gene pool over many generations ❖ Macroevolution = creation of new species (speciation) ❖ *Individuals don’t evolve, but populations do. ➢ Populations - all members of a species in a certain location ❖ Proof of Evolution ➢ Fossil Record - oldest fossils are of prokaryotes; transitional fossils exist that connect extinct fossilized species and modern ones ■ Fossils are dated through half-life of radioactive isotopes ➢ Comparative Anatomy ■ Homologous structures - shows common ancestry (ex. In the bat wing, whale flipper, human arm, function varies, but bone structure is the same.) ● Exemplifies divergent evolution ■ Analogous structures - similar ways of adapting; function is same, but structure is different (ex. Bat wing, fly wing) ● Exemplifies convergent evolution ■ Vestigial structures - exemplifies evolution in anatomy (ex. appendix) ➢ Comparative Biochemistry ■ Common ancestor = similar biochemical pathways ● More closely related = more similarities ➢ Comparative Embryology ■ Closely related = similar embryonic development ● Ex. Every vertebrate embryo has gill pouches at some point. ➢ Biogeography ■ Location of fossils can be evidence of common ancestor (ex. Marsupials) ➢ Molecular Biology ■ More closely related = more similar cytochrome c amino acid sequence Darwinian Theory of Natural Selection ❖ Populations of organisms often overpopulate until there are not enough resources ➢ This causes competition in order to survive. ➢ There is always variation in populations. ➢ Individuals that have more useful phenotypes have a greater chance of surviving/reproducing (survival of the fittest). These traits are passed down to future offspring. ➢ Evolution happens as the # of these helpful traits increase. ❖ Example 1: giraffe ancestors had short necks, with slight variations in length → giraffes with longer necks could reach more food and had greater chance of survival → more long-necked giraffes in population (individual giraffes didn’t change, population did) ❖ Example 2: dark moths had greater chance of survival after Industrial Revolution; frequency of dark moths increased in population ❖ Example 3: antibiotics killed most bacteria and resistant individuals survived/reproduced; next generation of bacteria was resistant to antibiotic Different Types of Natural Selection ❖ Stabilizing Selection - less extremes, more intermediate individuals (ex. Birth weight is mostly 6-9 pounds, not more or less since extremes are not as likely to survive) ❖ Disruptive Selection - more extremes, less intermediate individuals; causes ≥2 different phenotypes in a population (balanced polymorphism) and can create 2 new species. ❖ Directional Selection - one extreme dominates; a phenotype is completely replaced by another one (ex. Moths after Industrial Revolution) Causes of Diversity in a Population ❖ Mutations - random changes in DNA sequence ❖ Genetic Drift: change in available genes that happens because of chance ➢ Bottleneck Effect - reduction of population size without taking animal’s fitness into account (ex. Natural disasters); abnormally high/low # of certain alleles for genes ➢ Founder Effect - when small part of a population colonizes a new location; proportion of alleles differs from original population ❖ Gene Flow - when alleles move in/out of a population (often caused by migration of individuals/gametes to other populations) Requirements for Hardy-Weinberg Equilibrium ❖ Characteristics of NON-EVOLVING, stable population: ➢ Large population ➢ No gene flow / migration (isolated populations) ➢ No mutations ➢ Random mating ➢ No natural selection Hardy-Weinberg Equation ❖ Allows for calculation of allele frequency in a population (can be used for complex situations, but only simple (2 alleles) will be discussed. ➢ p + q = 1 or p2 + 2pq + q2 = 1 ➢ p is dominant allele, q is recessive allele Types of isolation that cause creation of new species ❖ Geographic Isolation - happens when species are separated (ex. Natural barriers like mountains, rivers, lakes, etc.) ❖ Polyploidy - mutation that happens due to mistakes during meiosis; polyploid individuals can only breed with other polyploid individuals ❖ Habitat Isolation - happens when organisms live in the same location but don’t usually meet (ex. One lives in water, one lives on land) ❖ Temporal Isolation - happens when organisms live in same location but reproduce/are active at different times ❖ Reproductive Isolation - inability to mate because of anatomical limitations (ex. Size difference) ❖ Behavioral Isolation - happens when animals are isolated because of varying behaviors (ex. Female fireflies only respond to blinking patterns of their own species) Evolution Patterns ❖ Convergent Evolution - is when unrelated species in similar environments have similar adaptations, or analogous structures (ex. Whale and fish) ❖ Divergent Evolution - is when a population is isolated and evolves into new species; the two species still have homologous structures (ex. human, bat, whale) ❖ Coevolution - is when two species that interact affect each other’s evolution (ex. Bee and flower) ❖ Parallel Evolution - is when two related species develop similar traits to adapt to similar environments (ex. North American gray wolf and Tasmanian wolf of Australia) ❖ Adaptive Radiation - when many species evolve from one common ancestor (ex. Finches in the Galapagos Islands) Various Theories of Evolution ❖ Gradualism - Darwin supported this theory; states that evolution happens over a long period of time and big changes happen when many small ones build up. ➢ Was disproven by fossil record ❖ Spontaneous Generation - states that living things come from nonliving/inanimate things; disproven ❖ Punctuated Equilibrium - most widely accepted; states that the appearance of new species is sudden and happens after long period of time without any change Important Facts ❖ *Earth is ~4.6 billion years old ❖ Heterotroph hypothesis - anaerobic heterotrophic prokaryotes were first cells ❖ Theory of endosymbiosis - eukaryotic cells formed when larger prokaryotes engulfed smaller ones and didn’t digest them ~1.5 billion years ago; these small prokaryotes became mitochondria/chloroplasts ❖ Mass Extinctions ➢ Permian mass extinction (250 million years ago) - happened when volcanic eruptions released lots of lava + carbon dioxide and almost wiped out life ➢ Cretaceous mass extinction (65 million years ago) - theory is that an asteroid crashed into Earth and caused a large debris cloud that blocked the sun (dinosaurs and many other animals went extinct). Biodiversity ❖ Every organism (living or extinct) is classified using taxonomy ➢ We still use binomial nomenclature, which was developed by Carl Linnaeus (ex. Homo sapiens); has genus name + species name ➢ Taxonomy builds off of evolutionary history, or phylogeny ➢ All organisms share certain traits, meaning that they all have a common ancestor that lived >3 billion years ago ❖ Most scientists today use the three-domain system (supported by analysis of DNA) ❖ Order of taxa (categories): domain, kingdom, phylum, class, order, family, species Domains ❖ Domain Archaea ➢ Single-celled + prokaryotic ➢ Introns are only present in some genes ➢ Extremophiles are in this domain: ■ Methanogens - get energy by making methane using hydrogen ■ Halophiles - can survive in places where concentration of salt is high ■ Thermophiles - can survive in places where temperatures are extremely high ❖ Domain Bacteria ➢ Unicellular prokaryotes ➢ Can be aerobic or anaerobic ➢ Are decomposers that recycle organic material ➢ Lots of them cause disease ➢ Some reproduce sexually (through conjugation) ➢ Can be heterotrophic or autotrophic ➢ Have thick cell walls ➢ No introns ❖ Domain Eukarya ➢ Have nucleus + organelles ➢ Has 4 kingdoms Kingdoms ❖ Kingdom Protista ➢ All are eukaryotes but vary a lot ➢ Most are unicellular, but others are simple multicellular organisms ➢ Can be heterotrophic (amoebas, paramecia) or autotrophic (euglenas) ➢ Move in different ways (amoeba = pseudopodia, euglena = flagellum, paramecium = cilia) ➢ Some can reproduce sexually through conjugation ➢ Includes seaweed + slime mold ➢ Can cause diseases ❖ Kingdom Fungi ➢ Eukaryotic heterotrophs ➢ Can be single-celled OR multicellular ➢ Releases digestive enzymes outside of cells to make nutrients easy to absorb ➢ Are decomposers and saprobes (get nutrients from rotting organic material) ➢ Cell walls made of chitin ➢ Can combine with algae to create photosynthetic lichens ➢ Reproduce asexually (budding, spores, fragmentation) and sexually ➢ Examples: mushrooms, yeast, mold ❖ Kingdom Plantae ➢ Multi-celled, autotrophic eukaryotes that can’t move around ➢ Cell walls made of cellulose ➢ Are photosynthetic and have chlorophyll ➢ Carbohydrates are stored as starch ➢ Reproduce sexually (alternation of generations; can be haploid gametophyte or diploid sporophyte) ➢ Some contain vascular tissue, some don’t ➢ Examples: flowering plants, ferns, moss ❖ Kingdom Animalia ➢ Multi-celled + heterotrophic eukaryotes that can move ➢ Usually sexual reproduction (often sperm and egg) ➢ Often classified by homologous structures + development of the embryo ➢ 35 phyla exist, but 9 are most common: porifera, cnidarians, platyhelminthes, nematodes, annelids, mollusks, arthropods, echinoderms, chordates Important Trends in Evolution ❖ Specialized Cells/Tissues/Organs ➢ Cell - basic unit of life (ex. neuron) ➢ Tissue - group of similar cells that have one specific function (ex. nerves) ➢ Organ - group of tissues that perform many functions (ex. brain) ■ Porifera: cells are not very specialized; don’t have true nerve/muscular tissues ■ Cnidarians: only simplest tissue forms ■ Flatworms: have organs; no organ system ■ Annelids + Arthropods: more complex; have organ systems ❖ Germ Layers ➢ Formed when embryo develops; eventually develop into tissues/organs ➢ Complex phyla have: ■ Ectoderm: outer layer; becomes nervous system + skin ■ Endoderm: inner layer; becomes digestive system (viscera) ■ Mesoderm: middle layer; becomes bones, blood, muscles ➢ *Porifera + cnidarians only have 2 cell layers (ectoderm and endoderm) which are connected by the mesoglea ❖ Cephalization ➢ Development of head/anterior + rear/posterior ■ Anterior: brain/ganglia, nerves ■ Posterior: digestive, reproductive, excretory organs/tissues ➢ No head is present in simpler animals (porifera, cnidarians) ➢ Complex animals all have a head ❖ Symmetry ➢ Most simple animals: radial symmetry ➢ Most complex animals: bilateral symmetry (mirrored left and right sides) ■ Echinoderms have bilateral symmetry when young but radial symmetry when older ❖ Formation of Body Cavity ➢ Coelom - cavity filled with fluid that is surrounded by mesoderm (is space for organ systems) ➢ Simple animals: no coelom; are acoelomates ■ Have flat bodies so every cell is in contact is environment ■ *Nematodes/roundworms are pseudocoelomates since they have tube between endoderm and mesoderm (hydrostatic skeleton) ➢ Complex animals: have coelom; are coelomates ■ Ex. Annelida, Mollusca, Arthropoda, Chordata Phyla ❖ Porifera (Sponges) ➢ Not symmetrical ➢ No muscle/nerve tissues + don’t move (are sessile) ➢ Water is drawn into vacity in the center; nutrients are filtered from it ➢ Have 2 cell layers (ectoderm + endoderm connected by mesoglea) ➢ Specialized cells are present; no tissues/organs ➢ Asexual reproduction (fragmentation) and sexual reproduction ❖ Cnidarians (Hydra, Jellyfish) ➢ Have radial symmetry ➢ Vase shaped (polyp) body which usually doesn’t move or medusa body which usually moves ➢ Some are have a larva stage and 2 reproductive stages: ■ Asexual (polyp) and sexual (medusa) ➢ 2 cell layers (ectoderm + endoderm connected by mesoglea) ➢ Digest food in a gastrovascular cavity (extracellular) or in lysosomes (intracellular) ➢ No transport system ➢ Have cnidocytes (stinging cells) ❖ Platyhelminthes (Flatworms/Tapeworms) ➢ Simple but have bilateral symmetry, a head, and 3 cell layers ➢ Only one opening for both eating + getting rid of waste ➢ No digestive/respiratory systems, so body is flat (nutrients/wastes can diffuse directly) ❖ Nematodes (Roundworms) ➢ Unsegmented ➢ Have bilateral symmetry ➢ Often parasitic ❖ Annelids (Segmented worms) ➢ Bilateral symmetry ➢ Tube for digestive tract (different parts are crop, gizzard, intestine) ➢ Excrete wastes through nephridia ➢ Has closed circulatory system ➢ Blood has hemoglobin + can carry oxygen ➢ Oxygen + carbon dioxide diffuses through skin ❖ Mollusks (Squids, Clams, Octopuses) ➢ Soft body (usually has hard shell) ➢ Open circulatory system ➢ Bilateral symmetry; three “zones” of body are: ■ Head-foot ■ Visceral mass - has digestive, excretory, and reproductive organs ■ Mantle - creates shell ➢ Has radula (functions similar to a tongue) ➢ Usually have gills + nephridia ❖ Arthropods (Insects, Crustaceans, Arachnids) ➢ Have joints ➢ 3 segments: head, thorax, abdomen ➢ Relatively large amount of sensory apparatus ➢ Have chitin exoskeleton ➢ Have open circulatory system ➢ Excretes nitrogenous wastes through malpighian tubules) ➢ Trachea (air ducts) bring in air ❖ Echinoderms (Sea stars, Sea urchins) ➢ Usually don’t move/move slowly ➢ Bilateral symmetry when young, radial symmetry as adult ➢ Reproduce sexually (fertilization outside body) or asexually (fragmentation or regeneration) ➢ Some have endoskeleton (sea stars) ❖ Chordates (Fish, Reptiles, Birds, Mammals, etc.) ➢ Have notochord ➢ Have a nerve cord that is hollow + dorsal ➢ Some have tail that helps animals move/balance ➢ Birds and mammals = homeotherms (stable body temperature) ➢ Other chordates = usually cold-blooded; sometimes endotherms Mammals ❖ Phylum is Chordata ❖ Provide milk to offspring (from mammary glands) ❖ Have hair + are warm-blooded ❖ Usually placental mammals (embryo develops in uterus + connected to mom by placenta) ➢ Marsupials are born extremely early ➢ Some mammals lay eggs (monotremes) Primates ❖ Includes humans ❖ Ancestors probably ate insects ❖ Have opposable thumbs ❖ Have nails and sensitive nerve endings in hands/fingers ❖ Eyes face forward + are close together ❖ Usually have few offspring per birth and care for them for long time ❖ Examples: humans, chimpanzees, gorillas, orangutans, etc. Cladograms/Phylogenetic Trees ❖ Branching diagram ❖ Represents hypothesis about evolutionary history of certain organisms