Chapter 22 Speciation

Question 1

What is needed for speciation to occur?how do new species form?

Answer 1

• for speciation to occur 2 new populations must be formed from 1 original population and they have to evolve so that it becomes impossible for the 2 new populations to interbreed
• new species form by being isolated and gene flow is currently off so the outcome is a unique history and interaction with the environment

Question 2

What is the difference between the morphological and the biological species concept? Why is the biological species concept a better definition for a species? What are the problems with the morphological species concept?

Answer 2

• morphological species concept says that this that look alike are the same species and those that look different are different species. This is misleading because males and females of the same species look different and species can look different in stages of life
• the biological species concept says that species successfully interbreed actively or potentially and produce fertile viable offspring

Question 3

What is needed to keep species apart once they form? What can lead to reproductive isolation?

Answer 3

• mechanisms that prevent successful interbreeding

- separation by distance or barriers, the gene flow gets cut off

Question 4

What is a sister species?

Answer 4

-a species that are each other’s closet relative, they have recent divergence, parallel speciation events among isolated lineages

Question 5

Explain allopatric speciation. What causes it and how does it lead to the formation of a new species?

Answer 5

• population is divided by a physical barrier(mountain range, body of water, distance) Changing environment
• new species form due to founder effect, members get isolated from main population and adapt to new environment
• cannot interbreed between groups

Question 6

Why is the founder effect an example of allopatric speciation?

Answer 6

-individuals get separated from a barrier and are isolated from a new group so they adapt and evolve

Question 7

Explain sympatric speciation. What causes it and how it leads to the formation of a new species.

Answer 7

• speciation occurring in the absence of a barrier, without physical isolation
• species diverge even though they can mate with each other but don’t because of behavioral change and chromosal # change

Question 8

Behavioral change and genetic change? What is polyploidy?

Answer 8

• behavioral change is the result of disruptive selection, species start to prefer other things like courtship, mating, or egg deposit
• genetic differences are like polyploidy in plants
• polyploidy the heritable condition of possessing more than 2 complete sets of chromosomes. Double number of chromosomes and can no longer interbreed with individuals having 2 sets

Question 9

Prezygotic barriers

Answer 9

• make it impossible for individuals to mate with each other, even before they are born
• examples: diff courtship behaviors between different animals(cricket song, bird dance)
• different reproductive timing (17 year cicada & 13 year cicada)
• habitat differences(snakes)
• physical differences( penis bones in diameter indents, shell spiral in snails)
• biochemical factors (chromosomal # difference, prevents successful fertilization)

Question 10

Postzygotic Barries

Answer 10

• occurs after fertilization
• mating between closely related species
• hybrid offspring
• prevent production of fertile offspring, they are unhealthy and don’t reach reproductive maturity
• examples: liger or Tygon are unhealthy because their body is not suited for their organs
• donkeys are strong hybrids but can’t reproduce