Option D2: Species and Speciation

Definitions• _________– all genes in a

population at a given time• _____- version of a gene• ____________– the

measure of a specific allele in proportion to the entire population

- Expressed as a proportion or _________

- Allele frequency is different than the number of _____________ in a population expressing that allele

Evolution of a species• Evolution of a species involves

a change in the ______________of a __________ over several generations

• Allele frequencies are only a __________

• __________, __________ or _______________ can occur (cause new entries into gene pool or exits from pool)

If suitable for _________, then gene will be passed on (increasing allele frequency)In time, previous less suitable genes will be “________” of gene pool

• _________ – any group of organisms that can reproduce fertile offspring

- Have similar ____________ (lineage)

- Have similar ____________________

- ____________ distinct from other organisms

What are some issues with this explanation of a species?

Barriers Between Gene Pools (How to get really weird animals and plants….)

• Genetic isolation– ____________________– islands,

mountain ranges, etc.– ___________ (reproductive) Isolation-

two species whose _______________do not intertwine ( pollen from one type of flower released before pistil of other flowers have emerged)

– _______________– mating behavior selects certain characteristics (mating ritual of one organism not seductive enough)

Any of these will lead to new __________ given enough time

Speciation

• Formation of a new ________ that no longer breeds with the ______________

Allopatric Speciation

• When speciation occurs because of _________________

• Islands are a great example of this

Sympatric Speciation• _________ do overlap, but

speciation occurs because of another influence (temporal, or behavioral)

• Could be mating ________, _______, or other courtship behavior

• ex. Mutation of pheremone that only attracts a few females

Polyploidy• Sex cells – __________• Somatic cells - __________• ______________ – condition where

there are more than 2 homologous chromosomes due to improper cell division

• Most common in __________ (makes them hardier)

• These extra chromosomes can make them _______________with the original. Can lead to _________ or ____________ of species if more favorable.

Adaptive Radiation• Many similar but distinct

species ___________ from one single species

• Happens when the organism is ___________ and in a ________ of opportunity

• In Darwin’s Finch the beaks adapted for ______ _____________

• Lemurs in Madagascar live in _______________ (desert, trees, ground)

Convergent vs. Divergent Evolution• Divergent is simply speciation due

to ____________ to new _____________ (ex. Ancestor squirrel split by grand canyon to White-tailed antelope sq. and Harris’s antelope sq.)

• Convergent Evolution is when different organisms evolve _______________ due to similar selective __________ (marsupial anteater in Australia; mammal anteater in S.A. bioluminescence in marine organisms and fungi)

Theories on pace of evolution• ___________ – species slowly

change through a series of intermediate forms

• Supporters say __________ for enough organisms exist to show these slow _________ changes

• Supporters also say that you don’t see most organisms ________________ now

• _______________ – rapid speciation due to new niche formation or geographic isolation

• Support by fossil record showing organisms (cochroaches, sharks) that have __________ significantly over millions of years

• Also supported by ______ in fossil record

Polymorphism

• When more than one ________ of a species is present in a population

• _________________– one form is distinctly disadvantaged

• __________________- if both forms provide a distinct advantage for survival

Transient Polymorphism

• Allele frequency changes in response to _____________

• Can change back

Sickle Cell Anemia is balanced polymorphism• In malaria stricken areas – both

forms offer a ________ (balanced)

• HbA allele codes for blood cells that __________, but susceptible to ___________

• HbS allele can’t carry O2, but __________ to malaria

• HbAHbS person gets best of __________

• When not in a location where malaria is endemic, not a suitable characteristic (transient)

• Cystic fibrosis• Cf gene causes _______

buildup, but normal gene is susceptible to ________