unit 8-natural selection Flashcards
evolution
a change in gene frequency over time
change of organisms over time
adaptation
trait shaped by natural selection that increases an organism’s reproductive success in a particular environment
descent with modification
identified hat species on earth today descended from ancestral species
natural selection
“survival of the fittest”
process where individuals that are best fit for their environment survive to reproduce
(the change in groups of organisms through time)
how old is the universe
15 billion years old
how old is the earth
4.5 billion years old
how long has there been life on earth
3.5 billion years
how long has there been humans
150,000 years
4 basics of natural selection
- individuals show a variety of genes
- variations pass from parent to offspring
- more offspring are produced than the environment can support
- variations that increase reproductive success will be more likely to be passed on
darwin’s
collected specimens and observed finches to develop two main points- descent with modification & natural selection
evidence for evolution
- the fossil record
- comparative anatomy
- comparative embryology
- comparative biochemistry
- geographic distribution
fossil record
chronological collection of life’s remains in the rock layer (old on bottom, new on top)
fossils
preserved remains of marking left by organisms that lived in the past
(found in sedimentary rock)
derived traits (newer)
newly evolved features (feathers)
they dont appear in the fossils of common ancestors
ancestral traits (older)
primitive reatures (teeth/ tails) appear in older fossils
comparative anatomy
relationship between the structure of ancient species and modern species
three parts of comparative anatomy
- homologous structures
- analogous structures
- vestigial structures
homologous structures
similar structures inherited by a common ancestor
Ex. arms/ wings
analogous structures
structures used for the same purpose and have similar features but aren’t inherited from the same ancestor
(Ex. wings- needed to fly but evolved separately)
vestigial structures
structures that are reduced forms of functional structures in organisms
(things that don’t really work anymore)
(Ex. human appendix)
comparative embryology
pre birth stage of an organisms development
(same during certain phases of development but become different structures in adults.
(Ex. humans and rabbits look alike as an embryo)
comparative biochemistry
the macromolecules organisms are made out of DNA, proteins, fats, carbs
the more DNA two organisms have in common, the more similar they are
(Ex. humans have 98% DNA common with chimps and 68% with moths which make us more similar to chimps)
geographic distribution
similar species of organisms that are geographically closer share more common characteristics
(patterns of migration explained the relationships)
biological fitness
measure of the relative contribution an individual trait makes to the next generation
(measurement of how many can reproduce)
population
a group of individuals of the same species living in the same area at the same time
what did Darwin realize in the Galapagos
- all species tend to produce excessively
- resources are limited.
variation
the differences among members of the same species
artificial selection
the selective breeding of domesticated plants and animals to produce offspring with genetic traits that human value
(Ex.dogs)
gene pool
all of the alleles in all the individuals that make up a polulation
microevolution
evolution on the smallest scale
generation change in the frequencies of alleles within a population
Hardy Weinberg principle
connection will not occur in a population unless allelic frequencies are acted upon by forces that cause change
equilibrium- p2+2pq+q2=1
5 conditions of the Hardy Weinberg principle
-population has to be large
-no immigration & emigration
-mating is random
-mutations do not occur
-natural selection does not occur
(to be at equilibrium, all conditions must be maintained)
genetic drift
any change in the allele frequencies in a population that is due to chance
types of genetic drift
founders effect & bottleneck
founders effect
small amount of organisms from a population become isolated from other populations. those traits are passed along which can lead to a change in frequency
bottleneck
when a population declines to a very low number
other causes of change in gene pools
- gene flow (an exchange of genes between populations)
- mutation