Unit 7: Natural Selection Flashcards
(AP key concepts)
When does speciation occur?
When population are reproductively isolated from each other.
What is the biological species concept?
Species are a group capable of interbreeding and exchanging genetic information to produce viable, fertile offspring.
What is punctuated equilibrium?
Evolution occurs rapidly after a long period of stasis, periods of minimal to no change.
What is gradualism?
Evolution occurs slowly over hundreds/thousands/millions of years.
What is allopatric speciation?
Evolution of new species through the process of geographic isolation over a long period of time.
What is sympatric speciation?
Evolution of a new species due to individuals being reproductively isolated from a surviving ancestral population.
How do pre-zygotic mechanisms impact speciation?
They prevent sperm and egg from meeting
How do post-zygotic mechanisms impact speciation?
They prevent a zygote from developing into a viable, fertile offspring.
What is speciation?
The creation of new species.
What does speciation result in?
Diversity of life forms.
What are the effects of allopatric speciation?
No gene flow. Exposes populations to different selection pressures.
What are the characteristics of sympatric speciation?
No geographic barrier. Can result from genetic mutations, polyploidy, habitat differentiation, and sexual selection.
What is the stimulus for evolution?
Changing ecological conditions.
What is adaptive radiation?
Evolution of new species that allows empty ecological roles or niches to be filled.
What factors lead to extinction?
Catastrophic changes to an ecosystem; Human activity; Invasive species.
How do environmental changes increase risk of extinction?
Mass destruction can result in habitat loss. Catastrophic events can wipe out many organisms.
How do speciation and extinction rates impact species diversity?
High species biodiversity can result from high levels of speciation and low levels of extinction and vice versa.
How does extinction create new niches?
When a species goes extinct, it leaves an open niche for another species to occupy.
What is extinction?
Complete disappearance of a species
What are the 5 pieces of evidence that support evolution?
geological- fossils; changes of environmental feature
geographical
physical- phenotypes
biochemical- chemical composition of living things
mathematic
How are fossils dated?
dated through age of rock
decay of isotopes
geological data
What demonstrates common ancestry for eukaryotes
membrane bound organelles
linear chromosomes
genes with introns
Lamarck Evolution
evolution through inheritance of acquired traits
Darwinian evolution
natural selection
–> mutation: longer neck giraffes survived and shorter neck died
What allows evolution?
Mutation–> favorable traits accumulating/ struggle for survival, inherited trait
what are the two types of dating for fossils?
relative: layer of soil fossil is found in
absolute:radioactive isotopes (carbon 14 decrease after death)
Define half-time
how much time it takes for half of carbon to disappear
Define homologous structures
organisms with genetically similar structures= common ancestor
common genes and similar anatomy but different environments and functions
Divergent evolution
common genes but different environments and purpose
define analogous structures
same function anatomically different; don’t share a common ancestor
define convergent evolution
don’t share a common ancestry
but developed similar functions
define endemic species
found in one place
embryology
vertebraes embryos look similar
define stabilizing selection
average/immediate phenotype was selection; extremes selected against
e.g. birthweight
define disruptive selection
extreme phenotype was selected and average against
define directional selection
one of the types of the extreme was selected
define sexual selection
females choose male that is more superior
name 10 sources of variation
mutations
diploidy
outrbreeding
sexual reproduction
gene flow
chromosomal mutations
nondisjunction
DNA mutations
transient polymorphism
balanced polymorphism
define diploidy
2 or more alleles
define outbreeding
mating with unrelated partners
gene flow
immigration/ emigration of individuals leaving or coming with diff. allele frequencies
define transient polymorphism
a phenotype dominant, but a new phenotype becomes more dominant due to environmental changes
define balanced polymorphism
maintenance of different phenotypes
e.g. carrier of sickle cell
conditions of hardy-weinberg equilibrium
- large population
- no mutation
- no gene flow of allees
- random mating
- no natural selectio
p=
frequency of dominant allele
p^2
frequency of homozygous dominant genotype
q=
frequency of recessive allel
q^2
frequency of homozygous recessive genotype
allopatric speciation
physical
ecological speciation
live in same region, different habitat
define temporal isolation
different mating seasons
behavioral speciation
courtship dance
mechanical isolation
mismatch genetalia
gametic isoation
gamete may not fertilize egg
origins of life explain
how organic compounds could come from inorganic precursors & then organic compounds undergoing further changes to form primitive cell-like structures
What did the urey-miller experiment do?
tested the origins of life hypothesis; shown under lab conditions can stimulate the conditions of early Earth & organic molecules from inorganic substances
RNA world hypothesis
a theory trying to figure out if DNA or RNA existed–> RNA came before DNA
define a niche
organism’s role in environment
define deleterious traits
traits that reduce chance of survival
