Origins of Species

Question 1

How do complex traits evolve?

Answer 1

• Advantageous intermediates (intermediate step might be advantageous in itself. Trait evolved by natural selection and improves an organisms ability to survive and leave descendants)
• Exaptation (Process by which features acquire functions for which they were not originally adapted or selected. Structure originally evolves for one purpose and then evolve further for another)

Question 2

What are the 2 types of speciation?

Answer 2

• Allopatric (vicariant or founder effect)

- Sympatric

Question 3

What is allopatric speciation?

Answer 3

• ancestral population geographically divided
• isolated subpopulations evolve reproductive barriers between them
• can occur two ways (vicariant and founder effect)

Question 4

What is Vicariant speciation?

Answer 4

• climate or geology causes populations to fragment
• fragments of the ancestral population are left intact
• fragmentation can occur in several species simultaneously
• Isthmus of Panama (land bridge that connects North and South America)
• Formed approx. 3,5 million years ago
• 30 species of snapping shrimp; genus Alpheus
  15 sister species on each side of the land bridge
• Many speciation events due to the same geographic barrier
• Land bridge caused geographical barriers which led to reproductive barriers

Question 5

What is the founder effect?

Answer 5

• occurs when a small number of individuals disperse to a distant place and form new populations

Question 6

What is sympatric speciation?

Answer 6

• diverging lineages co-occupy a geographic area

- different individuals within a species become specialized for occupying different components of the environment

Question 7

What is the biological species concept?

Answer 7

• characterizes species by their ability to interbreed to produce fertile offspring

Question 8

What is the morphological species concept?

Answer 8

characterizes species by body shape and other morphological features

Question 9

What is ecological species concept?

Answer 9

characterizes species in terms of its ecological niche

Question 10

Why are not all hybrids infertile?

Answer 10

• Interspecific hybrids (offspring produce by mating of individuals from two different species)
• Interspecific hybrids can sometimes be fertile and mate with another hybrid or other of their parental species

Question 11

What is a species?

Answer 11

• Bottom line: not easy to define
• The designation of species is a human construct
• No consensus, but most biologists would agree
  individuals descend from a common ancestral population
  reproductive compatibility
  genotypic and phenotypic cohesion