UNIT 2 DAY 8 - SPECIATION

Question 1

Speciation

Answer 1

new species arising from ancestral species

Question 2

Darwin’s theory of natural selection had fallen into disregarded by the early 20th century

Answer 2

• field biologists, the one who best understood adaptations in nature, favoured neo-lamarckian theories of species origins
  -lab centrered biologists favoured single-step, macromutational theories

Question 3

1930s natural selection was back

Answer 3

• fisher showed that natural selection worked perfectly with mendelian genes

Question 4

evolutionary synthesis

Answer 4

• fusion of Darwin and Mendel’s theories
• brought natural selection back to centre of evolution

Question 5

biological species concept

Answer 5

• emphasised species nature as evolving populations rather than as static types
• species are interbreeding populations that are reproductively isolated from other populationsn

Question 6

evolutionary biologists agreed that natural selection drives evolution (1940s)

Answer 6

• by accumulating many smal, favourable genetics variants over time each generated by random mutation, natural selection slowly and gradually alters a species in ways that adapt to its environment
• environment with competing species and physical conditions `

Question 7

microevolution

Answer 7

evolutionary change within a species or small group of organism, especially over a short period of time

Question 8

macroevolution

Answer 8

large-scale evolutionary changes that take place over long-periods of time

Question 9

reproductive isolation

Answer 9

• the inability of a species to breed successfully with related species due to geographical, behavioural, physiological or genetic barriers or differences

Question 10

geographic isolation

Answer 10

isolation between populations due to physical barriers

Question 11

how new species arise

Answer 11

1. how does a new species acquire its own, distinct set of traits
2. how does it become reproductively isolated from other species
3. are the answers to the first 2 questions related?

Question 12

Species

Answer 12

is a population (or a set of populations) with a distinct constellation of traits (grand Fact #1) that fit it to a particular ecological niche (Grand Fact #3). it remains distinct because it is reproductively isolated from other populations, breeding only with its own kind

Question 13

how does a new species acquire its own, distinct set of traits

Answer 13

• Darwin’s answer to the first question as his principle of divergence of character
• natural selection, he argued, drives the descendants of an original species into ever-divergent niches because the most divergent forms suffer the least competition
• gaps between species, makes them distinct

Question 14

how does it become reproductively isolated from other species?

Answer 14

• Mayr assumed that populations are somehow physically isolated as they diverge - either geographically or by habitat choice –> else they would interbreed and merge back into one
• Darwin expected diverging populations to lose the ability to interbreed even if they come back into contact

Question 15

reinforcement

Answer 15

• process by which selection can strengthen reproductive barriers
• selection will favour individuals who mate within their own population because they will avoid having unfit hybrids and over time, stronger and stronger pre-mating reproductive barriers will evolve, yielding 2 distinct species

Question 16

allopatric speciation

Answer 16

the process of speciation that occurs with geographic isolation

Question 17

allopatry

Answer 17

occurs in separate, non-overlapping geographic areas

Question 18

sympathy

Answer 18

occurring in the same geographic area

Question 19

prezygotic barriers

Answer 19

prevent mating or fertilisation between species

Question 20

temporal isolation (prezygotic)

Answer 20

mating or flowering occurs at different seasons or times of day

Question 21

habitat isolation (prezygotic)

Answer 21

populations live in different habitats and do not meet

Question 22

behavioural isolation (prezygotic)

Answer 22

there is little or no sexual attraction between species

Question 23

mechanical isolation (prezygotic)

Answer 23

structural differences in genitalia or flowers prevent copulation or pollen transfer

Question 24

gametic isolation (prezygotic)

Answer 24

male and/or female gametes die before uniting or fail to unite

Question 25

postzygotic barriers

Answer 25

prevent the development of fertile adults

Question 26

reduced hybrid viability (postzygotic)

Answer 26

hybrids zygotes fail to develop or fail to reach sexual maturity

Question 27

reduced hybrid fertility (postzygotic)

Answer 27

hybrid fails to produce functional gametes

Question 28

hybrid breakdown (postzygotic)

Answer 28

offspring of hybrids are weak or infertile

Question 29

niche partitioning

Answer 29

by changes in beak size and shape that allow each species to occupy a different niche

Question 30

5 possible outcomes of 2 populations being initially isolated and then regaining contact

Answer 30

1. Niche overlap/ no reproductive barrier
2. no niche overlap/ no reproductive barrier
3. niche overlap/reproductive barrier
   4.no niche overlap/ partial reproductive barrier
4. partial niche overlap/ reproductive barrier

Question 31

Diploid

Answer 31

2 alleles/genes

Question 32

haploid

Answer 32

one allele/gene