Evolution: (How Species Form)

Question 1

What is a species?

Answer 1

•species:
•interbreed.
•produce viable offspring.
•reproductively isolated from other species.
•eg. Elephants and frogs cannot interbreed…

Question 2

Forming a new species:

Answer 2

•speciation: the formation of a new species.

Question 3

Two pathways for speciation:

Answer 3

•transformation: new species gradually develop as a result of mutation and adaptation to changing environmental conditions.
-old species is gradually replaced.
•divergence: one or more species arises from a parent species.
-increases biological diversity because it increases the number of species.
-adaptive radiation.

Question 4

Adaptive radiation:

Answer 4

•adaptive radiation: diversification of a common ancestral species into a variety of species, all of which are differently adapted.
•ex. Galapagos islands finches.
•various selective pressure resulted in different feeding and mating habits, as well as different physical differences of birds.

Question 5

Keeping populations separate:

Answer 5

•for speciation to occur, two populations must be prevented from interbreeding.
•populations must be isolated from one another through:
1. Geographical barriers.
2. Biological barriers.

Question 6

1. Geographical barriers:

Answer 6

•Physical separation.
•ex. Mountains and rivers.
•prevent interbreeding because populations are physically separated.
•isolation does not have to be maintained forever for speciation to occur.

Question 7

2. Biological barriers:

Answer 7

•reproductive isolation.
•when species can not produce viable offspring because:
1. Physical incompatibility.
2. Different behaviours (bird vs. frog song).
3. Different pheromones (spider mate attraction).

Question 8

Biological barriers (2):

Answer 8

•Eastern and Western Meadowlarks are two distinct species, even though their habitats overlap.
•they have distinctively different songs.

Question 9

The pace of evolution:

Answer 9

•2 models that scientists have proposed for the pace of evolution based on the fossil record:
1. Gradualism.
2. Punctuated equilibrium.

Question 10

1. Gradualism:

Answer 10

•gradualism: gradual change occurs steadily in a linear fashion.
•big changes occur as a result of the sum many small changes.

Question 11

2. Punctuated equilibrium:

Answer 11

•punctuated equilibrium: model proposes that evolutionary history consists of long periods of equilibrium where there is little change and “punctuated” or interrupted periods of speciation.
•such speciation events often follow periods of mass extinction, resulting in the next generation being very different from the original.

Question 12

What is a theory?

Answer 12

Theory: a scientific theory is a scientific prediction that has a lot of backed up evidence. That is why it is hard to disprove them.