Lecture 20

Question 1

What is a species?

Answer 1

• Biological species concept
• Morphological traits species concept
• Common ancestor: phylogenetic species concept

Question 2

Reproductive isolation? and its limitations

Answer 2

Reproductive isolation: is the existence of biological factors (barriers) that impede 2 species from producing viable, fertile offspring
- Reproductive isolation restricts gene flow b/w 2 species.

Limits to this definition:
Can’t be used for species that reproduce asexually or that are extinct.
To know if reproductive isolation exists, need to know all the breeding partners of the species in question, but can’t know for sure who breeds with who in nature. (see bear example)
Gene flow can sometimes occur between distinct species (see hybrids)

Question 3

Prezygotic & postzygotic barriers lead to reproductive isolation definition?

Answer 3

Barriers prevent interbreeding b/w 2 different species whose living ranges overlap.
If living ranges don’t overlap, no need for a barrier.

Question 4

Prezygotic barriers

Answer 4

Prevent fertilization ie formation of a zygote

Question 5

postzygotic barriers

Answer 5

Reduce viability or fertility of the hybrid

Question 6

what are Prezygotic barriers?

Answer 6

• Habitat isolation
• Temporal isolation
• Behavioral (sexual) isolation (Distinctive courtship behaviors prevent mating between species)
• Mechanical isolation (Structural differences in the reproductive organs of similar species) In animals Often reproductive organs “don’t fit”
• gametic isolation (Gametes from different species are incompatible: sperm of 1 species can’t fertilize eggs of another species)

Question 7

what are some POSTzygotic barriers ?

Answer 7

• Hybrid inviability
• Hybrid sterility
• Hybrid breakdown

Question 8

Hybrid inviability?

Answer 8

Death of interspecific embryos during development.

Ex If artificially fertilize bullfrog eggs with leopard frog sperm: almost all hybrids die in embryonic stage

Question 9

Hybrid sterility?

Answer 9

Hybrids can’t reproduce successfully

Can’t do meiosis so can’t make gametes: sterile

Question 10

why are mules sterile?

Answer 10

no homologous chromosomes

Question 11

Hybrid breakdown?

Answer 11

Offspring of hybrids do reproduce, but only for a few generations

Question 12

Morphological species concept?

Answer 12

A species is a group of organisms with similar structure (morphology) & behavior.

Question 13

Phylogenetic species concept

Answer 13

The smallest group of individuals that share a unique common ancestor and who all possess a unique set of morphological or genetic traits.

Question 14

Patterns of Speciation, how do new species rise?

Answer 14

• New species arise by evolution of ancestor species

- New species arise by hybridization of 2 different species

Question 15

Allopatric speciation VS Sympatric speciation

Answer 15

Allopatric speciation: Start with 2 separate populations of the same species → evolve into 2 separate species

Sympatric speciation: Start with 1 population (same species) → evolve into 2 separate species

Question 16

Allopatric speciation

Answer 16

• Habitat isolation occurs : pre-zygotic reproductive barrier b/w groups
• Each population exposed to different selective pressures, genetic drift, +/or mutation that cause micro-evolution
• Eventually, 1 or both populations undergo enough genetic changes that results in the formation of permanent reproductive barrier

Question 17

sympatric speciation

Answer 17

In sympatric speciation, speciation takes place in geographically overlapping populations

Sympatric speciation can occur if gene flow is reduced by factors including:

Mutations
Habitat differentiation
Polyploidy

Question 18

Paedomorphosis

Answer 18

juvenile characteristics are kept in the adult

Causes big changes in the behavior

Question 19

Polyploidy?

Answer 19

the presence of extra chromosome sets due to errors during cell division (mitosis or meiosis)
many sets of chromosomes

Question 20

__% of all plants are polyploids

Answer 20

25-50

Question 21

__% of flowering plants are polyploid

Answer 21

80

Question 22

How do polyploids arise?

Answer 22

NON-DISJUNCTION

Question 23

allopolyploidy ?

Answer 23

a polyploid individual or strain having a chromosome set composed of two or more chromosome sets derived more or less complete from different species.

Question 24

Hybridization: Species A + B =

Answer 24

species C

Question 25

3 possible outcomes of a new species In same environment as “parent species”

Answer 25

1. New species may not survive if not well adapted: becomes extinct
2. New species coexists with parent species
3. New species survives better than 1 or both parents: may even replace the parent species

Question 26

Possible outcomes as a species diverges:

Answer 26

1. reinforcement: Hybrids stop forming. Two separate species
2. fusion: Two “species” fuse into one
3. stability: Hybrids keep forming

Question 27

species may be identified by the __& __aspects

Answer 27

Biological Morphological

Question 28

Biological species concept based on __ caused by __ and __

Answer 28

Reproductive isolation

prezygotic barriers and postzygotic barriers

Question 29

Morphological species concept based on __

Answer 29

distinct body structures.

Question 30

Species may originate by __ and __ in which __

Answer 30

Allopatric speciation and Sympatric speciation

gene flow is interrupted

Question 31

gene flow interrupted in allopatric speciation between _

Answer 31

geographically isolated populations

Question 32

gene flow interrupted in Sympatric speciation by _

Answer 32

Mutations- sexual selections
Habitat differentiation
Polyploidy

Question 33

species may interbreed in __ which may result in __, __ and ___.

Answer 33

hybrid zones

fusion of species, stable hybrid zone, reinforcement (reproductive barriers.)

Question 34

which concept of speciation is most commonly used

Answer 34

BSC Biological species concept

Question 35

where can speciation occur

Answer 35

Can occur in different environments (allopatric), or in a shared environment (sympatric)

Question 36

Speciation Can be due to ?

Answer 36

Can be due to changes in genomes of a single ancestor or can be due to hybridization.

Question 37

10 reproductive barriers

Answer 37

Prezygotic barriers
Postzygotic barriers
Habitat isolation
Temporal isolation
Behavioral (sexual) isolation
Mechanical isolation
gametic isolation
Hybrid inviability
Hybrid sterility
Hybrid breakdown