chapter 24: origin of species

Question 1

what is speciation

Answer 1

• one species splits into two or more

- produced diversity and explained why organisms share features (unity)

Question 2

microevolution

Answer 2

changes over time in allele frequencies in population

Question 3

macroevolution

Answer 3

• broad pattern of evolution above the species level

- origin of new groups of organisms

Question 4

what is a species

Answer 4

• group of population whose members have the potential to inbreed in native and produce viable fertile offspring
• BUT DO NOT with other members of such groups
• united by being reproductively compatible

Question 5

gene flow

Answer 5

• transfer of alleles between populations

- occurs between different populations

Question 6

reproductive isolation

Answer 6

-existence of biological factors (barriers) that impede members of two species from interbreeding and producing viable, fertile offspring

Question 7

how does reproductive isolation limit hybrid formation

Answer 7

-offspring from interspecific mating are unable to mate due to barriers that isolate their gene pools

Question 8

prezygotic barriers (“before zygote”)

Answer 8

• block fertilization from occurring

- will prevent attempted mate from being completed successfully or will hinder fertilization if mating is successful

Question 9

post zygotic barriers (“after zygote”)

Answer 9

• contribute to reproductive isolation after hybrid zygote is formed
• developmental problems may reduce survival or problems after birth may cause infertility or decrease chance of reproducing

Question 10

limitations of biological species concept

Answer 10

• knowledge of mating habits are required
• only works for sexually reproducing organisms
• many obviously different species do hybridize successfully in nature

Question 11

morphological species concept

Answer 11

• distinguishes species by body shape and other structural features (sexual/asexual)
• disadvantage is that it relies on subjective criteria

Question 12

ecological species concept

Answer 12

• defined in terms of ecological niche which is the sum of how members of the species interact with the nonliving and living parts of the environment (asexual/sexual)
• emphasizes role of disruptive natural selection as organisms adapt to environment

Question 13

allopatric speciation (“other country”)

Answer 13

• gene flow is interrupted when population is divided into geographically isolated subpopulations
• new species forms in geographic isolation
• geographic barrier splits a population into subpopulations

Question 14

how does allopatric speciation work?

Answer 14

• the organism can only move if geographic barriers allow them too
• separated gene pools diverge after separation
• can cause new mutations, natural selection, genetic drift, and reproductive isolation

Question 15

evidence of allopatric speciation

Answer 15

• regions that are isolated by barriers typically have more species
• reproductive isolation generally increases when geographic distance increases

Question 16

sympatric speciation (“same country”)

Answer 16

• occurs in populations that live in the same geographic area (less common)
• can occur if gene flow is reduced by polyploidy, sexual selection, and habitat differentation

Question 17

polyploidy

Answer 17

-accident during cell division resulting in extra set of chromosomes (common in plants)

Question 18

what are the two types of polyploidy

Answer 18

• autopolyploid

- allopolyploid

Question 19

autopolyploid

Answer 19

• more than two chromosome sets all from single species
• 3n or 4n number
• reduced fertility in hybrids

Question 20

allopolyploid

Answer 20

• more than two sets of chromosomes from different organisms
• can successfully mate with each other but not with either parent species

Question 21

habitat differentiation and sympatric speciation

Answer 21

-sympatric speciation can result from appearance of new ecological niches

Question 22

hybrid zone

Answer 22

-region in which members of different species meet and mate producing at least some offspring of mixed ancestry

Question 23

why do allele frequencies change across hybrid zones?

Answer 23

• obstacles to gene flow

- hybrids may have higher risk of mortality or abnormalities

Question 24

where are hybrid zones located

Answer 24

• where habitats of the interbreeding species meet

- form when two species lacking barriers come into contact

Question 25

how do environmental conditions alter interbreeding

Answer 25

• can alter where the species meet
• hybrid zone can allow for genetic variation that improves ability of one or more species ability to adapt to changing environmental conditions

Question 26

3 possible outcomes of hybrid zone over time

Answer 26

1. reinforcement (strengthens reproductive barriers)
2. fusion (weakens reproductive barriers where species fuse into one)
3. stability (continued formation of hybrid individuals)

Question 27

punctuated equlibria

Answer 27

used to describe periods of apparent stasis punctuated by sudden change

Question 28

do organisms have speciation clock

Answer 28

• no

- do not have anything to tell them to produce new species at irregular levels

Question 29

when does speciation occur?

Answer 29

• after gene flow is interrupted by changing environment condition or unpredictable events
• populations must become geographically isolated after gene flow is interrupted

Question 30

what does the evolution of reproductive isolation result from? (genetics of speciation)

Answer 30

• effects of single gene or small number of genes
• mutation at single locus can contribute to reproductive isolation
• speciation may be influenced by larger number of genes