evolution
intro to evolution
individual- 1 organism
population- group of individuals of the same species that live in the same area and reproduce with one another
not a change in an individual
change in a population over time
micro-evolution
evidence for evolution
patterns in the fossil record
amino acid sequences (even when dna sequences are slightly different)
pattern of anatomical similarities
dna sequences
pattern of embryological similarities
mechanisms
migration
genetic drift
mutation
natural selection
change in dna
random (beneficial, harmful, or neutral)
aka gene flow
movement of individuals (and their genetic information) from one population to another
some individuals leave descendants by chance
unlike natural selection, an advantageous trait is not necessarily being selected for
occurs because there is variation, heredity, and the environment cannot sustain unlimited population growth
caring capacity
change in gene frequency within a population
occurs over short periods of time, like from one generation to the next
macro-evolution
small changes build up over millions of years
patterns we see when cooking at the large-scale history of life
evolution above the species level
life on earth has been accumulating small changes for 3.8 billion years
fossil evidence
transitional form
organisms that show the intermediate states between an ancestral form and that of its decedents
relative dating
comparing fossils ages by where they are found in the earth (superposition)
radioactive dating
radioactive elements in fossils or sediments surrounding fossils (EX: radioactive carbon to nitrogen in 60,000 years)
comparative anatomical evidence
homologous structures
similar structures in related organisms that are a result of common ancestry
vestigial structures
little or no purpose to present organisms, but provide evidence for common ancestry
homologous vs. analogous
homologous
characters in different organisms that are similar because they were inherited from a common ancestor that also had that character
common ancestry/decent- when one species is the ancestor of two or more species later in time (EX: forelimbs of tetrepods, humans, whales, birds, etc.)
analogous
have seperate evolutionary origins, but are superficially similar because they have both experienced natural selection that shaped them in a similar way
converent evoloution- process in which two distinct lineages evolve a similar characteristic independently of one another (EX: flight in birds vs. flight in birds)
embryological evidence
homologous structures observed during early embryological development
these homologous structures may not be visible in the fully developed organism
molecular evidence
dna sequences
amino acid sequences
chromosomes
gene expression (which genes are turned on and off/ the timing of when genes are turned on and off
mutation
...can all be compared to determine relativeness of organisms (EX: we can lean about the evolution of humans and our closest living relative, the chimpanzee, by comparing chromosomes
a change in a dna sequence (usually occurring because of errors in replication or repair)
the ultimate source of genetic variation
random
can be beneficial, neutral, or harmful, for the organism, but mutations do not "try" to supply what the organism "needs"
the only mutations that matter to large- scale evolution are those that can be passed on to offspring (occur in reproductive cells like eggs and sperm and are called germ line mutations)
migration/gene flow
migration= gene flow
movement of individuals, and their genetic material, from on population to another (EX: pollen being blown to a new destination, people moving o new cities or countries)
if gene versions are carried to a population where those gene versions previously did not exist, gene flow can be a very important source of genetic variation
sex can introduce new gene combinations into a population and is an important source of genetic variation
natural selection
variation of traits
heredity
carrying capacity (differential reproduction= not all individuals get to reproduce to their full potential
when the above 3 criteria are met, evolution by natural selection will is occurring
adaption
a feature that is common in a population because it provides some improved function
adaptive radiation
a single species evolves into a number of other species
these species are distinct from one another but are closely related
each species is specialized for a different environment (fills a different niche)
sexual selection
acts on an organisms ability to successfully copulate with a mate
sexual selection makes many organisms go to extreme lengths for sex
sexual selection is often powerful enough to produce features that are harmful to the individuals survival
EX: extravagant and colorful tail feathers or fins are likely to attract predators as well as interested members of the opposite sex (peacock tails, birds of paradise, and elephant seals fighting for territory)
artificial selection
people (instead of nature) select which organisms get to reproduce
farmers and breeders allow only the plants and animals with desirable characteristics to reproduce
EX: produce, pets, and livestock
co- evolution
cases here two (or more) species reciprocally affect each others evolution
likely to happen when different species have close ecological interactions with one another
EX: predator/ prey & parasite/ host, competitive species, mutualistic species
speciation
species= a population of similar organisms that can interbreed to produce viable, fertile offspring
speciation is a lineage- splitting event that produces two or more seperate species
branching points on phylogenetic trees are seperation events
geographic isolation is an important step of some speciation events
microevolution=small scale, single population
macroevolution= grand scale, across species