evolution paletzki

evolution

the cumulative change in the heritable characteristics of a population

heritable characteristics are encoded by

genes and are transferred by alleles

evolution requires a ___ of change and a consequential ___ for change

source, mechanism

sources of change may include

genetic mutations and chromosomal abnormalities, sexual reproduction and meiosis, and gene flow (migration)

mechanisms for change may include

random events (genetic drift), directional forces (natural selection or artificial selection)

germline mutations

occur in sex cells and can be passed to offspring

crossing over

DNA segments are exchanged between homologous pairs (meiosis)

independent assortment

separation of the homologous pairs is random (meiosis)

random fertilization

the fusion of two haploid gametes is also random (meiosis)

gene flow

describes the movement of alleles between different populations

gene flow can alter the diversity of a population via

immigration or emigration

how does gene flow create variation

by introducing genes from an alternative population source

populations that are in close proximity will show

less variation (less divergence)

distant populations typically show a

greater level of variation

genetic drift

a change in the composition of a gene pool due to chance events

genetic drift is greater when the population is

smaller (more prone to change)

natural selection as a mechanism for change

a change in the composition of a gene pool as a result of the presence of differentially selective environment pressures

artificial selection as a mechanism for change

humans determine the favorability of a particular trait (may involve selective breeding or transgenic techniques)

speciation

the formation of a new and distinct species in the course of evolution

what leads to speciation

mechanisms of change will reduce variation and increase the degree of genetic divergence between geographically isolated populations

speciation occurs when

populations cannot interbreed and produce fertile offspring

scientific theory

a well supported explanation of how the world works

scientific evidence

evidence which serves to either support or counter a scientific theory or hypothesis

evidence for evolution can be demonstrated by identifying

similarities in unrelated organisms (common ancestry)

evidence for evolution can be demonstrated by showing

a change in characteristics between current and ancestral species

evidence for the process of evolution include:

fossil records, comparative anatomy, selective breeding, biogeography, and DNA (molecular)

fossils

the preserved remains or traces of organisms from the remote past

fossil record

totality of fossils (discovered and undiscovered)

law of fossil succession

over time changes occurred in ancestral organisms, with different species appearing within the fossil record in a systematic order

conditions required for fossilization to occur

preservation of remains, exposed to high pressure to promote mineralization, subjected to anoxic (low oxygen) conditions to prevent decomposition

how can fossils be dated

according to the age of the rock layer (strata) in which they are found

relative age

estimates the age of the fossil by looking at where the fossil is in the rock layer

absolute age

use isotopes and half-lives to determine a more accurate age of the fossil

transitional fossils

any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group

homologous structures

share a common basic structure despite being used in different ways

adaptive radiation

when a single species or small group of species rapidly diversifies into many new species (ex. darwin’s finches)

vestigial structures

Structures that have no apparent function and appear to be residual parts from a past ancestor

why are vestigial structures evidence of evolution

they suggest that an organism changed from using the structure to not using the structure

comparative embryology

studies the similarities and differences in the embryonic development of different species to understand evolutionary relationships and how animal body plans originated

selective breeding

a form of artificial selection where humans breed animals w/ desirable characteristics to increase the frequency of these traits

why is selective breeding evidence of evolution

it leads to exaggeration of these traits in domesticated animals compared to their wild counterparts

biogeography

the distribution of life forms over geographical areas

why is biogeography evidence of evolution

related species tend to be in close physical proximity

how is molecular (DNA) evidence of evolution

DNA comparisons between species suggest how closely related they are, the more similar an organism’s DNA is to another the more closely related they are

evolution

the cumulative change in the heritable characteristics of a population

gene pool

a combination of all the genes (including alleles) present in a reproducing population or species

large gene pool

higher levels of genetic diversity

gene pool compositions change over time

genetic drift + natural selection

allele frequency

the prevalence of a particular allele in a population of organisms. it is calculated as a percentage of the alleles in a gene pool

bottleneck effect

when an event reduces population size by an order of magnitude, the surviving population is smaller and has less genetic variability (greater genetic drift)

founder effect type

when a new population is established by a small subset of a larger population (resulting in less genetic variation and greater genetic drift)

stabilizing (type of natural selection)

an intermediate phenotype is featured over the extremes

directional (type of natural selection)

one phenotypic extreme is selected at the expense of another

disruptive (type of natural selection)

both extremes are selected over an intermediate phenotype

hybrid

an offspring of two animals or plants of different subspecies, breeds, varieties, species, or genera

pre-zygotic

occurs before fertilization can occur

temporal mechanism

populations differ in periods of activity or reproductive cycles (pre-zygotic)

behavioral mechanism

populations exhibit different specific courtship behaviors (pre-zygotic)

geographic mechanism

populations occupy different habitats or niches within a region (pre-zygotic)

post-zygotic

occurs after fertilization

hybrid inviability mechanism

hybrids produced but fail to develop to reproductive maturity (post-zygotic)

hybrid infertility

hybrids fail to produce functional gametes (post-zygotic)

hybrid breakdown mechanism

F1 hybrids are fertile, but F2 generation fails to develop properly (post-zygotic)

allopatric speciation

divergence due to geographical isolation

sympatric speciation

divergence within same geographical location

phyletic gradualism

speciation results from continuous change occurring at a constant pace

punctuated equilibrium

speciation results from abrupt bursts that intersperse periods of stability

r-strategist

many offspring, short energy/time for raising and producing, frequently changing habitat, short lives (ex. mouse)

k-strategist

few offspring, lots of energy/time for raising and producing, stable environment, long lives (ex. humans)

william paley

wrote a book called ‘natural theology’ which influenced darwin

what ship did darwin go on

the HMS beagle, traveling south america, australasia, and africa

charles lyell

darwin read his theories while on the HMS beagle, learning that the Earth's features were formed by gradual, ongoing geological processes, not catastrophic events. 

thomas robert malthus

darwin read his essay on the principle of population, who’s arguments were the final clue for darwin: a relationship between the environment and the reproduction of populations

alfred russel wallace

sent a letter to darwin in 1858, wallace had also discovered natural selection and they published a joint letter.

john baptiste lamarck

incorrectly theorized that evolution happened by acquired characters. (ex. giraffes would stretch their necks to reach trees, get longer necks, then pass on the long necks to their offspring0

james hutton

used geology to prove the world was much older than just a few thousand years old

analogous structures

structures with different origin and structure but are adapted for the same purposes are called

four points of darwin’s theory of evolution

overproduction, variation, adaptation, and selection