BZ110 exam 1

Principles of Animal Bio:

• Traits that all animals have in common:

  • Eukaryotic (they have nuclei in their cells)

    • Key difference between pro & eu is the presence of a nucleus and mitochondria, which are only found in eukaryotes. Additional differences include membrane structure, ribosome structure, how transcription & translation work, presence or absence of specific genes/other organelles

  • Multicellular

  • Specialized tissues

    • Atoms → molecules → organelles → cells → tissues → organs, organ systems

  • Heterotrophic (eat organic matter)

  • Breathe oxygen

  • Capable of motility

  • Can reproduce sexually (can also reproduce asexually)

  • Members of the kingdom Animalia, and descendants of the common ancestor of all animals

    • Over 1.4 million animal species are described. Most animals (69%) are insects, around half of that are beetles

• What is science?

  • A system for organizing and generating knowledge through use of the scientific method

  • Seeks to understand what is true about the universe

  • But… science cannot answer all questions, only scientific questions

Evolution: 

• Evolution: 

  • A change in the heritable characteristics of biological pops over successive generations

  • Ecology & evolution are closely related in a feedback loop. Ecology sets the state that evolution acts in, but evolution can change the stage itself too

    • While biotic ecological changes (like community composition and pop density) are likely to affect evolutionary change, they are not the same thing as evolutionary change

  • Ancestral species → descendent species with new traits that arise

  • 2-step process: (1) genetic variations among individuals in a pop, (2) proportions of variant types change from gen to gen

• Heritable vs non-heritable characteristics:

  • Heritable: height, natural hair color, eye color

  • Non-heritable: may affect an individual’s bio fitness but are not ‘evolvable’

• Allopatric isolation: pop divergence due to pop being geographically separated

  • Dispersal: part of pop independently moving 

  • Vicariance: some geological event that separates the pop

• Sympatric speciation: pops diverge but live in the same geographic area

  • Prezygotic barriers: when making a zygote is somehow inhibited (including habitat, temporal, behavioral, mechanical, gametic isolation)

  • Postzygotic barriers: can’t produce fertile offspring but can produce offspring (includes reduced hybrid viability & fertility, hybrid breakdown)

• Misconceptions & realities of NS:

  • Selection acts on individuals, but actually, pops evolve

  • Selection is not forward-looking nor predictive (it acts on current variation under current conditions

  • Speciation doesn’t act for the good of the species, nor do new adaptations arise bc species need them (survival of the fittest) → new adaptations don’t arise bc species need them

    • Adaptations can arise bc they’ll be favored by selection & spread, but it’s not guaranteed to happen

  • Selection only acts upon existing traits – cannot create a new trait, even if it’s beneficial

  • Selection doesn’t lead to perfection (there’s still trade-offs, changing environment)

  • Evolution isn’t anti-religion; it acts on a continuum

• Historical context: before darwin, species were thought to be static & not evolve

  • Lamarck: acquired characteristics can be inherited (now discredited)

  • Darwin & Wallace: proposed that organisms with advantageous traits are more likely to survive & reproduce; these traits become more common in the pop over gens (called “descent with modification”)

• Genetic basis & adaptation: 

  • Variation: evolution requires genetic variation, originating from mutations & sexual reproduction (mutations can be beneficial, neutral, harmful)

  • Adaptation: traits that enhance survival & reproduction are adaptations

• Patterns of evolution:

  • Divergent evolution: common ancestor → evolve in different directions

  • Convergent evolution: similar structures arise through evolution independently in different species

• Modern synthesis – integration of genetics: combines NS & genetics; describes how evol pressures can affect a pop’s genetic makeup and can result in the gradual evol of pops, species

  • Microevolution: gradual change in a pop over time 

    • Small scale changes within pops – describe the process that explains patterns

    • Changes in allele frequencies over time

  • Macroevolution: processes that rise to new species & higher taxonomic groups with widely divergent characteristics

    • Large scale changes observed above the spies level

    • Describes a pattern that arises from the process; descent with modification

  • → speciation: the process of a population diverging into two descendant species. Helps to link microevolution to macroevolution

• Population genetics: how selective forces change allele frequencies in a pop over time

  • Allele frequencies: NS, mutation, genetic drift, gene flow alter allele frequencies

  • Mechanisms of microevolution: 

    • NS: advantageous phenotypes are more likely to reproduce & survive

      • Removes individuals (or genes) on the basis of certain traits\

      • Step 1 – only acts on preexisting variation; step 2 – change due to differences in fitness

    • Mutation: source of new alleles in a pop; changes in DNA sequences

      • Step 1 – mutation is genetic change & mutations introduce new variation; step 2 – mutation is/isn’t passed onto following gens

    • Genetic drift: random change in the frequency of gene variants in a pop over time; when allele frequency changes – due to random chance

      • Step 1 – only acts on preexisting variation; step 2 – change due to randomness or sampling error

      • Bottleneck effect: catastrophic event that results in a large portion of the gene pool dying (could be natural disaster or human actions). Surviving pop is no longer representative of original pop

      • Founder effect: when a few individuals become isolated from a larger pop and establish a new pop (new pop will likely have a gene pool that differs from the original pop)

    • Gene flow: flow of alleles in & out of a pop resulting from migration

      • Step 1 – only acts on preexisting variation between pops, but could bring new variation into a focal pop; step 2 – change due to migration

  • Hardy-Weinberg equilibrium: the principle that states that allele frequencies remain constant in absence of evolutionary forces; deviations indicate evolution

• Evidence for evolution: 

  • Fossils: show pattern of gradual change over time

  • Anatomy & embryology: presence of structures in organisms that share same basic form

    • Homologous structures: anatomical features in different species that have a similar underlying structure due to common evolutionary origin

    • Vestigial structures: were once functional for ancestors, now reduced/nonfunction

  • Biogeography: geographic distribution of organisms shows patterns of evolution

  • Molecular bio: molecular structures reflect descent with modification

• Speciation: 

  • Speciation: formation of 2 species from one original species (can interbreed and create fertile offspring)

• Mechanisms of speciation:

  • Allopatric speciation: speciation in ‘other homelands’, involving geographic separation of pops from a parent species & subsequent evolution

    • Geographic barriers create separate environment with different selection pressures; genetic divergence leads to reproductive isolation over time

  • Sympatric speciation: speciation in the ‘same homeland’, speciation in the same location; happens within a single geographic area where pops become reproductively isolated despite sharing the same habitat

    • Polyploidy: involves an error in chromosome number during cell division; can result in a new species that cannot interbreed with parent species 

    • Ecological niche differentiation: individuals exploit different resources or habitats within the same area, leading to reproductive isolation

• Adaptive radiation: rapid diversification of a single ancestral species into a wide range of forms that occupy different ecological niches. Typically occurs when a species colonizes a new environment with various available niches or after a major extinction event

Phylogeny & Taxonomy:

• Phylogeny: pattern of evolutionary history among species

  • Root: base of the tree; represents ancestral lineage

  • Time: moves forward from the root

  • Nodes: most recent common ancestor

    • Nodes can rotate, but evol relationships don’t change

  • Branches: evolutionary paths

  • Tips: taxon at present time

  • → lineage: continuous line of descent from ancestor to descendant

  • Clade: nested group that includes common ancestor & descendants

(aka monophyletic group)

• Cladogenesis: splitting of ancestral lineage into descendent lineages, forms clade

• Most Recent Common Ancestor (MRCA): last common ancestor; inferred from last divergence (node)

• Homologous vs analogous:

  • Homologous: characteristics you share with other species because you got them from a common ancestor (similarities in structure between 2+ species, inherited from CA)

  • Analogous: characteristics that appear to be similar between 2+ species but they arose independently (not genetically related?)

• Derived v ancestral:

  • Shared derived: shared but it evolved more recently

  • Shared ancestral: shared but arose in a common ancestor

• → ALL OF THIS IS RELATIVE to what’s on the tree & when it starts

  • Taxonomy is the same as tree thinking, but more broadly arranged

• Monophyletic groups: aka clade

  • 2+ species, including common ancestor & all of its descendents 

  • How to identify & describe groups of species on a phylogeny tree

• All taxonomic names (kingdom, phylum, class, order, family, genus, species) should be nested monophyletic groups… phenetic names = nicknames & taxonomic names = legal names

Earth History:

• The earth is ~4.54b years old (4.54 x 10^9)

• Geologic time scale: eon → era → period → epoch

• Hadean eon: 4.54-4 bya

  • Earth forms (“hell on earth”)

  • Moon forms following impact by Mars-sized proto-planet ~60 my after earth is formed

  • Late heavy bombardment of earth (by asteroids) ~4.1-3.8bya

• Archean eon: 4-2.5 bya

  • Origin of life ~3.8-3.5bya

  • Anoxic photosynthesis ~3.4bya

  • Oxygenic photosynthesis at least ~2.4bya, potentially earlier (simple, prokaryotic life)

  • Lots of rain & oceans form; longest eon

• Proterozoic eon: 2,500 bya-542 mya

  • Great oxidation event ~2.2bya

  • Eukaryotes (cells with a nucleus evolve) ~1.8bya

  • Ancestors of plants & animals become multicellular ~800 mya

  • Ediacaran period ~635-542 mya

    • Small, sessile filter feeding animals

    • Jellyfish and other cnidaria

• Phanerozoic eon: 542 mya-today

  • Divided into 3 eras: paleozoic (521-251 mya); mesozoic (251-66 mya); cenozoic (66 mya-today)

  • Each era is divided into multiple periods; each period divided into multiple epochs

  • Only represents ~12% of earth’s history

• → the eons of the phanerozoic eon:

  • Paleozoic era: 

    • Cambrian period: 542-488 mya

      • “Cambrian explosion” – explosion of complex life (more nutrients in the water due to land erosion & flooding; complex ecosystem with more predators evolving; more oxygen entered the water - more nutrients)

      • Nearly all major animal phyla evolve (hard skeletons, shells)

    • Ordovician period: 488-444 mya

      • First non-vascular plants

      • Bony jawless fish arise, the first vertebrates

      • Arthropods on land (insects & shit)

      • Ends with ordovician-silurian mass extinction

    • Silurian period:444-416 mya

      • First vascular plants on land

      • First jawed fish arise

      • Huge coral reefs form

    • Devonian period: 416-359 mya

      • First fish with teeth

      • Vertebrates move onto land, first amphibians

      • Wood & early seed plants evolve

    • Carboniferous period: 359-299 mya

      • Large forests of lycophytes, ferns, and primitive seed plants

      • First conifers arise; first tetrapod herbivores; giant insects

      • Diversification of winged insects, first dragonflies, giant insects

      • Oxygen hits peak of >30% of atmosphere (today its 21%); most forests we see today were formed in this period; most coal is from this period

      • Starts warm & humid, ends cold & dry bc of tons of photosynthesis

    • Permian period: 299-251 mya

      • Seed plants & conifers diversity; first beetles; first therapsids (mammal-like reptiles)

      • Pangea supercontinent; ended with largest mass extinction in earth’s history (almost wiped out all of life, lots of volcanic eruptions)

  • Mesozoic era:

    • Triassic period: 251-200 mya

      • First turtles & dinosaurs; cycads and conifers diversify

    • Jurassic period: 200-146 mya

      • Pangea breaks up

      • Archaeopteryx and other feathered dinosaurs arise

      • Lepidopters (moths, butterflies) arise & pterodactyls (flying dinosaurs) diversify; dinosaurs become dominant vertebrates

    • Cretaceous period: 146-66 mya

      • Flowering plants evolve; first social bees, termites, ants

      • Time of tyrannosaurus & triceratops

      • Marsupials and placental mammals evolve

      • Ends with K-T extinction

  • Cenozoic era:

    • Paleogene period: 66-23 mya

      • Grasses evolve & grassland ecosystems start to form

      • Modern bird groups diversify; ungulates (hoofed mammals) evolve

    • Neogene period: 23-2.6 mya

      • Continents near modern distribution

      • Lots of mammal diversity; first marine mammals start evolving; first hominins

    • Quaternary period: 2.6 mya-today

      • First hominin tool use (~2.5 mya); Homo erectus (~1.8-0.07 mya); Homo neanderthalensis (~350k-30k ya); Modern homo sapiens (~300kya)