Please enable JavaScript.
Coggle requires JavaScript to display documents.
BIO120 Lecture 3: Darwin's Evidence for Evolution + Chapters 2-4…
BIO120 Lecture 3: Darwin's Evidence for Evolution + Chapters 2-4
Geology
Found fossils of mammals that no longer existed
Discovery of transitional fossils later on justifies this
Steno's principle of superposition considered strata from all around the world to compile geological record (not all layers are present in one area) --> gave relative ages of rocks --> radiometric dating later used to give actual age of rocks
Outcome:
Earth is old --> long time for evolution / gradual changes
Intermediate forms provide evidence of common ancestors linking features of living organisms
Fossils in younger strata must resemble modern species more; remodeling old into new
Fossil formation requires specific conditions, so fossil record is highly incomplete
Organism has to sink to ocean floor
Sediment covers organisms, preventing decay/consumed by scavengers
Hard parts become replaced by dissolved minerals --> forming cast (soft parts aren't fossilized easily --> know less about worms, jelly fish, bacteria, etc.)
Cast compressed by pressure of sediments
Discovered when sediments are exposed by wind or rain erosion
Homology: patterns of similarity among organisms that reflect common ancestry
Vestigial organs: feature that was ancestors' adaptation but has either lost its usefulness or been co-opted for new uses (NOT functionless, just no longer performs what it was originally adapted for)
Flightless ostriches/emus/kiwis
Blind cavefish live in caves
Human appendix was important to leaf-eating ancestors; discovered to provide refuge for gut bacteria when infection removes them from digestive system
Goosebumps are indicative of tiny muscles attached to base of body hair that contract in response to cold or adrenaline
Atavisms: sporadically expressed remnants of ancestral features via re-expression of formerly functional genes that have been silenced by natural selection
Whales contain genetic information for making legs
Human embryos have tail that almost always disappears
Tissue lining from mouse's jaw into chicken --> molecules from mouse reawaken dormant development program for making teeth in chickens
Dead genes/pseudogenes: once useful but no longer intact or expressed
GLO makes vitamin C from glucose in other organisms (primates missing pathway due to inactivation possibly caused by ample vitamin C in diet)
Many olfactory receptor genes have been silenced in humans --> recognize less airborne molecules (each gene produces different protein/olfactory receptor); proof that dolphins evolved from land mammals as they contain OR genes
Monotremes (platypus) are only mammals that have active egg-laying gene
Biogeography: study of species distribution; comparing molecular clock w/ continental movement
Adaptive radiation: evolution of phenotypic diversity within rapidly multiplying lineages as result of speciation --> exploitation of unoccupied niches
Trait utility
Rapid speciation
Recent common ancestry from single species
Correlation b/t phenotype and environment
Convergent evolution - organisms of different species experience similar selective pressures, causing them to undergo similar adaptations
Geographically isolated areas have unusual organisms
Ex. Australia flora and fauna (such as marsupials) have high levels of endemism
Oceanic islands tend to lack fish/reptiles/mammals/amphibians, which continental islands all have (what they DO have are in abundance, though, despite lack of variety)
Geographically close organisms resemble each other
Ex. Galapagos islands colonized by species capable of long-distance dispersal
Species on oceanic islands are most similar to those on nearest mainland
Different organism groups adapt to similar environments in different areas
Domestication
Large amounts of heritable variation
Variation can be selected on --> dramatic changes
Evidence in the present
Antibiotic resistance, herbicide resistance, adaptation to pollution
Natural selection in the wild
Genomic evidence for vestigial traits
Advances in geology to estimate age of strata
Transitional fossils have traits that make them look like descendants of earlier ones
Fossils have types of traits that link two groups together + dating evidence matches estimated time
Transitional species are not ancestral species (simply shows mixture of traits from organisms that lived before and after it)
Saw splitting of species and discovery of ancestors (e.g. reptile fossils became more mammal-like as mammals evolved from reptiles)
Ex. Tiktaalik roseae (fish --> amphibians) showed visual features of fish but also features that allowed it to breathe above surface
Ex. Archaeopteryx (theropod dinosaurs --> birds) had reptilian features and large feathers (evolved before flight, possibly for attracting mates, insulating, etc.); exhibited bird-like sleeping behaviours
Trees-down scenario - feathery forelimbs helped glide --> escape predators, find food, cushion falls
Ground-up scenario - flapping helped give extra propulsion --> airborne hops
Fossils in adjacent layers were more similar (gradual process of divergence)
Columnar core w/ thick slices of rocks pulled from seafloor, containing single species
Environments not preserved so selective pressures not identified
Formation of new species occurs b/c of geographic isolation
Forms of life appear in order of evolutionary sequence
All vertebrates begin development looking like embryonic fish and follows evolutionary sequence (some parts disappear, others change)
Proof that descendants inherit developmental programs of its ancestors
Structures that form later require biochemical cues (proof of adding new onto old rather than remodeling)
Poor and imperfect design comes from evolutionary heritage
Human laryngeal nerve
Women give birth through pelvis b/c infant's head became too large due to brain size BUT pelvis opening has to remain narrow for bipedal walking