Speciation

Question 1

What is speciation?

Answer 1

the origin of new species, is at the key point where microevolution and macroevolution intersect

Question 2

How many species exist?

Answer 2

Known: 2-3 million
Estimated: 5-100 million

Question 3

What is a species?

Answer 3

Members of a biological species are reproductively compatible, at least potentially; they cannot interbreed with other populations

Question 4

How do new species originate from existing ones?

Answer 4

A reproductive barrier to gene flow is established, making the populations diverge genetically (allele frequencies) and making them reproductively isolated

Question 5

What is reproductive isolation?

Answer 5

the existence of biological factors (barriers) that impede two species from producing viable, fertile hybrids

Question 6

What is the biological species concept?

Answer 6

Species are groups of actually or potentially inbreeding populations, which are reproductively isolated from other such groups

Question 7

What are prezygotic barriers?

Answer 7

Temporal or Habitat Isolation- potential mates don’t meet
Ethological, Behavior, or Sexual Isolation- potential mates meet but do not mate
Mechanical Isolation- Copulation occurs, no gamete transfer
Incompatibility- Gametes are transferred, no fertilization

Question 8

What are postzygotic barriers?

Answer 8

Hybrid Inviability- Fertilization occurs, but F1 hybrid has reduced viability
Hybrid Sterility- F1 hybrid viable, but has reduced fertility
Hybrid Breakdown- Reduced viability/fertility in F2 or backcross hybrids

Question 9

What are the premating barriers?

Answer 9

Temporal or Habitat Isolation, Ethological, Behavioral or Sexual Isolation

Question 10

What are the postmating barriers?

Answer 10

Mechanical Isolation, Incompatibility, Hybrid Inviability, Hybrid Sterility, Hybrid Breakdown

Question 11

What are some limitations of the biological species concept?

Answer 11

Can’t be applied to fossils
Can’t be applied to asexual organisms
Some organisms are morphologically and ecologically distinct, yet interbreed

Question 12

What is the morphological species concept?

Answer 12

Morphological species concept- characterizes species by body shape and other structural features

Question 13

What is the ecological species concept?

Answer 13

Ecological species concept- characterizes species in terms of their ecological niches

Question 14

What is the phylogenetic species concept?

Answer 14

Phylogenetic species concept- defines a species as the smallest group of individuals that share a common ancestor, forming one branch of the tree

Question 15

What is allopatric speciation?

Answer 15

A population forms a new species while geographically isolated from its parent population
ex: snapping shrimp and Hawaiian fruit flies

Question 16

What is sympatric speciation?

Answer 16

A subset of a population forms a new species without geographic seperation

Question 17

What can cause sympatric speciation?

Answer 17

habitat differentiation (usually through selection)
Polyploidy (mutation)
Sexual selection (blue and orange fish example)

Question 18

How does sympatric speciation via autopolyploidy occur?

Answer 18

Both chromosome sets are derived from the same species

Question 19

How does sympatric speciation via allopolyploidy occur?

Answer 19

The chromosome sets are derived from different species

Question 20

What are hybrid zones?

Answer 20

Regions where members of different species with incomplete reproductive barriers mate and produce hybrids

Question 21

What are the possible outcomes of hybrid zones?

Answer 21

Reinforcement (natural selection increase reproductive isolation, strengthen reproductive barriers)
Fusion (the species interact with each other again, weaken reproductive barriers)
Stability (no change in species interactions, continued formation of hybrid individuals)

Question 22

What does the flowers example represent in respect to speciation?

Answer 22

In other organisms, speciation can be influenced by larger numbers of genes and gene interactions

Question 23

What is the tree of life?

Answer 23

Idea that all organisms on earth are related to each other via a gigantic tree of common descent