Origins of Species Flashcards
1
Q
How do complex traits evolve?
A
- 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)
2
Q
What are the 2 types of speciation?
A
- Allopatric (vicariant or founder effect)
- Sympatric
3
Q
What is allopatric speciation?
A
- ancestral population geographically divided
- isolated subpopulations evolve reproductive barriers between them
- can occur two ways (vicariant and founder effect)
4
Q
What is Vicariant speciation?
A
- 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
5
Q
What is the founder effect?
A
- occurs when a small number of individuals disperse to a distant place and form new populations
6
Q
What is sympatric speciation?
A
- diverging lineages co-occupy a geographic area
- different individuals within a species become specialized for occupying different components of the environment
7
Q
What is the biological species concept?
A
- characterizes species by their ability to interbreed to produce fertile offspring
8
Q
What is the morphological species concept?
A
characterizes species by body shape and other morphological features
9
Q
What is ecological species concept?
A
characterizes species in terms of its ecological niche
10
Q
Why are not all hybrids infertile?
A
- 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
11
Q
What is a species?
A
- 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