Evolution Lecture 5

Question 1

Darwin’s Origin of species?

Answer 1

It’s answers where the many species on earth come from and how come there is so many. Darwin saw speciation when he went to the islands and saw species similar to the ones on the mainland.

Question 2

Species

Answer 2

Difficult to make universal definition. But typically it’s related organisms that share common characteristics and are capable of interbreeding.

Question 3

Morphological species concept

Answer 3

Based on morphological (physical) similarity. Historically, most commonly used concept. How much difference is enough (it’s very subjective)? It’s unity within a species. Extinct animals are described by this.

Question 4

Morphological species concept example?

Answer 4

Two intents that look mostly the same but have one major difference. How do you know it’s a new species and not just a new population of a species that’s already been made.

Question 5

Ecological Species Concept

Answer 5

Views a species in terms of its ecological niche, the sum of how members of the species interact with the nonliving and living parts of the environment.

Question 6

Molecular Sequence similarity

Answer 6

Looking at the DNA sequence but it’s also subjective.

Question 7

Biological Species Concept

Answer 7

Separateness of a species. Can a set of organisms reproduce to sexually produce viable, fertile offspring. Species are designated by the absence of gene flow. Based on inter-fertility, not similarity. Not always applicable, but usually most useful concept (eg, can’t work with asexual organisms.

Question 8

Inter-fertility

Answer 8

Populations that interbreed to produce fertile offspring. They are a species if they can do this.

Question 9

Reproductive Isolation

Answer 9

Do not normally successfully interbreed in nature with other species = No/few ‘Hybrids.’ Not the same species.

Question 10

Hybrids

Answer 10

One parent in one population and one in the other. They are often less fit than parent species.

Question 11

Speciation

Answer 11

The making of new species. Makes diversity. Forms the bridge between micro and macro evolution.

Question 12

Clade agenesis

Answer 12

When one species becomes two.

Question 13

Anna genesis

Answer 13

Where one species changes so much that you wouldn’t think it was the same species.

Question 14

Reproductive barriers

Answer 14

Inhibit gene flow between populations, allowing evolutionary divergence. Feature of its biology that prevent them with breeding with one another.

Question 15

Speciation event

Answer 15

Where new species arise (the branch points on the tree of life).

Question 16

Prezygotic Barriers

Answer 16

Acts before fertilization that blocks it.

Question 17

Postzygotic barriers

Answer 17

Acts after fertilization. Prevents a healthy, fertile adult offspring.

Question 18

Example of Prezygotic Barriers (in order of the chain)?

Answer 18

Habitat Isolation (live in different habitats)
Temporal Isolation (breed at different times)
Behavioural Isolation (have different mating cues)
Mechanical Isolation (tried, but won’t form a zygote)
Gametic isolation (gamete incompatibility)

Question 19

Liger example?

Answer 19

Hybrid that grow to adult and typically are fertile. Not found in nature (a lot of barriers between them).

Question 20

Example of Postzygotic Barriers (in order of the chain)?

Answer 20

Hybrid inviability (Zygote has a low chance of surviving adulthood because of genes)

Hybrid infertility (sterility) (It becomes an adult but is infertile)

Hybrid breakdown (they are viable and fertile offspring but when they mate with one another the offspring will be sterile)

Question 21

Mules example?

Answer 21

Bred by famers to pull things. They are infertile. Since they are descended from a common ancestor, there is change in the arrangement of genes on chromosomes. So the chromosomes don’t pair properly when put together, during meiosis when you try and pair up those chromosomes get massive non-disjunction.

Question 22

Evolution of reproductive barriers?

Answer 22

May arise ‘accidentally’ as result of evolution in isolation (two lineages become separate species and reproductive barriers evolved as a consequence of other evolutionary change (adaptive to different environments).

May evolve through natural selection to reduce inter-species mating that lowers reproductive success.
(e.g. ‘Reinforcement’) (Where there is existing barriers to reproduction (post), you can get the additional pre barriers, through natural selection).

Question 23

Two ways of speciation?

Answer 23

Allopatric and Sympatric

Question 24

Allopatric speciation

Answer 24

Geographic barrier blocks gene flow between populations. It’s more common. Barriers to reproductive evils while they aren’t experiencing gene flow.

Question 25

Geographic barriers

Answer 25

Features of landscape that separate populations physically.

Question 26

Example of geographic barriers for land animals?

Answer 26

Rivers, Seas between islands or continents, Mountain ranges

Question 27

Example of geographic barriers for sea animals?

Answer 27

Landmasses. Isthmus of Panama that isolated population of marine species when it formed.

Question 28

Evolution after separation?

Answer 28

Natural selection to different environments (i.e. adaptive evolution). Genetic drift (especially in small isolated populations). The founder effect on species from mainland to island, island becomes new species with no gene flow (peripheral isolates).

Question 29

How can we tell allopatry has occurred?

Answer 29

Unless they come together again and can breed together again. Many things could happen when they reform and it depends how viable and fertile the hybrids are.

Question 30

If contact re-established between evolved allopatric populations (2 things)?

Answer 30

Complete reproductive barriers evolved: Populations now classic biological species (two disinct species) Partial reproductive barriers evolved: Formation of hybrids where species contact.

Question 31

Hybrid zones

Answer 31

Located wherever the habitats of the interbreeding species meet. Environment conditions can alter the habitats of interbreeding species meet.

Question 32

Fusion

Answer 32

Hybrids form readily; have high fitness: the incipient species merge into one again. Have gene flow and weakening reproductive barriers.

Question 33

Reinforcement

Answer 33

Hybrids have low fitness: Natural selection strengthens barriers - Hybridisation gradually ends = Two good Biological Species. Strengthing of reproductive barriers.

Question 34

Long-lasting Hybrid zone

Answer 34

Hybrids have variable fitness or are uncommon. Hybrids are continued to be produced.

Question 35

Species formed on the tree of life?

Answer 35

It takes a lot of time, it's not sudden like it shows.

Question 36

Introgression

Answer 36

Hybrids that breed back with one of the new species can introduce alleles from the other species. Opportunities for genes pass from one species to another. Important for understanding genetic makeup of many populations around. Incomplete separation of species.

Question 37

Sympatric speciation

Answer 37

Requires a barrier to gene flow within a geographic region. Requires some mechanism to generate a barrier to gene flow. Can be done by sexual selection.

Question 38

Habitat differentiation

Answer 38

Where genetic factors are enable a subpopulation to exploit a habitat or resources not used by the parent population.

Question 39

Examples of Sympatric speciation?

Answer 39

Host switching by specialist herbivores or parasites. Disruptive selection: favouring evolution of reproductive barriers between individuals with different phenotypes? Polyploid speciation, especially in plants.

Question 40

Autopolyploid

Answer 40

Where it mates with itself and has a cell division failure doubling the # of chromosomes so new species is made.

Question 41

Polyploid speciation (Allopolyploid)

Answer 41

Where two species with different # of chromosomes mate and produce viable but infertile hybrid. But then mitotic error double the chromosome number so now it's fertile. But it's unlikely it will find another one like it, so it can't sexually produced. Van't produce with either parent. So it uses stealthing to start a new population. This is an example of hybrid speciate and is common in plants and an exception to a strict "tree-of-life."

Question 42

Speciation and tree-of-life?

Answer 42

Each branching on the tree-of-life began with a speciation event.