Speciation : Biology

Question 1

Speciation

Answer 1

Formation of new species from common ancestors. (Branching effect)

Question 2

Microevolution

Answer 2

Evolutionary change within a species or small groups over a short period of time. (Changes in the frequency of a gene in a population, different dogs breeds from gray wolf) (small scale)

Question 3

Macroevolution

Answer 3

Formation of new species. Individuals split from river, form multiple generations, river dries and are connected again, because of genetic differences individuals can no longer interbreed. (two beetle species) (large scale)

Question 4

How are speciation events depicted on trees?

Answer 4

The root of the tree represents the ancestral lineage, and the tips of the branches represent the descendants of that ancestor. As you move from the root to the tips, you are moving forward in time.

Question 5

Reproductive Isolation

Answer 5

The inability of a species to breed successfully with related species due to geographical, behavioral, physiological, or genetic barriers or differences.

Question 6

Prezygotic Isolation

Answer 6

Blocks fertilization from occurring by (1) preventing different species from attempting to mate.

Question 7

Prezygotic Isolation Mechanisms

Answer 7

1. Habitat Isolation
2. Temporal Isolation
3. Behavioral Isolation
4. Mechanical Isolation
5. Genetic Isolation

Question 8

Habitat Isolation

Answer 8

Two species rarely or never encounter one another due to occupying different habitats despite no physical barrier isolation. (Gryllus pennsylvanicus prefers sandy soil, while Gryllus firums prefers loamy soil.)

Question 9

Temporal Isolation

Answer 9

Species that breed at different times of the day, different seasons, or different years.
(Eastern spotted skunk mates late winter
Western spotted skunk mates late summer.)

Question 10

Behavioral Isolation

Answer 10

Courtship rituals and other behaviors unique to a species are effective barriers to mating. (Blue footed boobies and albatross only mate after unique species specific courtship display.)

Question 11

Mechanical Isolation

Answer 11

Morphological differences can prevent successful completion of mating. (In plants, difference in flower shape or structure prevent pollination, Two species of snails genital openings are not aligned and mating cannot occur.)

Question 12

Gametic isolation

Answer 12

Sperm of one species may not be able to fertilize eggs of another species.
(Red and purple sea urchins release egg and sperm into surrounding water but zygote will not form because proteins on surface of gametes will not fuse together.)

Question 13

Postzygotic Isolation

Question 14

Postzygotic Isolation Mechanisms

Answer 14

1. Reduced hybrid viability
2. Reduced hybrid fertility
3. Hybrid breakdown

Question 15

Reduced hybrid viability

Answer 15

Genes of different parent species may impair hybrid’s development or survival in its environment. (Salamander species sometimes hybridize but most zygotes do not complete development and those that survive to offspring are usually frail and die.)

Question 16

Reduced hybrid fertility

Answer 16

Even if hybrids are vigorous, they may be sterile. (Male Donkey + female horse = mule which is sterile)

Question 17

Hybrid breakdown

Answer 17

A type of reproductive failure that appears after the F2 generation of crosses between different species or subspecies. Some 1st generation hybrids fertile, but when hybrids mate w/ each other or with either parent species offspring feeble or sterile. Deleterious recessive alleles occur. (Hybrid rice with stunted offspring)

Question 18

What are the 2 modes of Speciation?

Answer 18

1. Allopatric
2. Sympatric

Question 19

Allopatric

Answer 19

Population divided into two, geographically isolated subpopulations. (Geographical Isolation, animals on opposite sides of mountain)

Question 20

Sympatric

Answer 20

Populations living in the same geographical area. (Reproductive Isolation, barriers reduce gene flow, huge wooded area)

Question 21

Adaptive Radiation

Answer 21

When a single ancestral species gives rise to a variety of species, each adapted to a specific environment. (From a grass lizard all the way to a Iguana high up in the trees.)

Question 22

Mass extinction

Answer 22

Large numbers of species become extinct worldwide. (5 mass extinctions in fossil record over past 500 million years)

Question 23

What are 1/2 major Mass Extinctions?

Answer 23

Permian Extinction 252 mya

Extreme volcanic eruptions produced CO2 warmed global atmosphere by 6°C
Series of catastrophes
Lava (100s m thick) covered 1.6 million km2 in Siberia
96% of marine species went extinct

Question 24

What are 2/2 major Mass Extinctions?

Answer 24

Cretaceous extinction 66 mya

Created the Chicxulub crater off coast of Mexico
Left thick layer of iridium-enriched clay
Blocked sunlight
Disturbed global climate
Mass extinction of:
>50% of marine life
All dinosaurs (except birds)

Question 25

Are we presently in out 6th extinction?

Answer 25

Today’s extinction rates suggest we are in our 6th. (1000 lost in last 400 yrs, huge factor is climate change, Anthropogenic = caused by humans)

Question 26

Relationship between species extinctions and humans population growth.

Answer 26

As the human population increases, so do the number of species extinctions. Direct correlation. (Up to 8700 species extinctions per year based on computer modeling.)