Lecture 4- Species and their formation I

Question 1

What is the name of the system of Latinate nomeclature that species are named by and who created this system?

Answer 1

Binomial system, Carolus Linnaeus

Question 2

Classifying animals based on their appearance is called…

Answer 2

the morphological species concept

Question 3

Why do members of many groups look alike?

Answer 3

Because they share many alleles that code for their body structure.

Question 4

What is a limit of the morphological species concept?

Answer 4

Not all members of a species look alike- males, females, young individuals

Question 5

Define speciation.

Answer 5

The process by which one species splits into two or more daughter species, which there after split into distinct lineages

Question 6

What is an important process that leads to speciation?

Answer 6

Reproductive isolation- individuals of a population do not mate with individuals of another population- they become distinct evolutionary units

Question 7

Ernst Mayr proposed what concept in 1940?

Answer 7

The biological species concept

Question 8

What is the biological species concept?

Answer 8

Species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups

Question 9

To which organisms does the biological species concept not apply to?

Answer 9

Asexually reproducing organisms

Question 10

What do evolutionary changes lead to?

Answer 10

Potentially nothing- a single species may change over time without giving rise to a new species.
If evolutionary changes results in splitting into two or more daughter species, speciation occurs.

Question 11

What is a requirement of speciation?

Answer 11

Gene flow within a population whose members formerly exchanged genes is interrupted.

The two populations must become isolated, sufficient differences in their genetic structure accumulate during this isolation until they cannot exchange genes when reunited.

Question 12

What are the two main types of speciation?

Answer 12

Allopatric speciation,

sympatric speciation

Question 13

What is allopatric speciation?

Answer 13

Also known as geographic speciation

Speciation that results when a population is divided by a physical barrier

Question 14

What is the most dominant mode of speciation among most organisms?

Answer 14

Allopatric speciation

Question 15

What physical barriers may divide species during allopatric speciation?

Answer 15

Mountain ranges, dry land, bodies of water

Question 16

What processes can generate physical barriers between populations?

Answer 16

Glacial advance/ retreat, continental drift, climate change, sea level rise

Question 17

Why do separated populations evolve differences?

Answer 17

Genetic drift

Environmental changes

Question 18

Explain how particular Finch species are an example of members of an existing population crossing existing barriers to create a new, isolated population. (Allopatric speciation)

Answer 18

Dawin’s Finches- 14 species of Finch living on the Galapagos archipelago- 1000 km off the coast of Ecuador.
These arose from a single South American species that colonised the islands
The islands distances from each other means that Finches rarely disperse among them, and they have different environmental conditions (flad and arid, mountain slopes)
Populations have differentiated so that the genetic distinctiveness and cohesiveness of the species are maintained

Question 19

How do we know that species of the Drosophilia flies on the Hawaiin islands were founded by dispersing individuals?

Answer 19

The closest relatives of a species on one island is often a species on a neighboring island rather than a species from the same island. Studies of chromosomes of picture-winged Drosophilia flies shows that speciation in this group resulted from 45 founder events

Question 20

What determines a physical barriers effectiveness?

Answer 20

Size and mobility of the species in question

Question 21

Define sympatric speciation.

Answer 21

A partition of the gene pool without physical isolation

Question 22

What type of disruption is required for sympatric speciation?

Answer 22

Disruptive selection (such as in Black-bellied seed crackers)

Question 23

Explain disruptive selection in Rhagoletis pomonella

Answer 23

• Hudson river valley, New York state
• Until 1850’s mating and egg laying occurred on Hawthorn fruit
• Larvae learned odor as they fed
• Commercial apple orchids
• Eggs were laid by mistake on apples
• Larvae learned new odor
• Now there are two distinct groups on their way to speciation

Question 24

What are the different types of sympatric speciation?

Answer 24

Ecological isolation

Polyploidy (autopolyploidy, allopolyploidy)

Question 25

What is polyploidy?

Answer 25

The production within an individual of a duplicate set of chromosomes

Question 26

What is autopolyploidy?

Answer 26

Chromosome duplication in a single species

Question 27

What is allopolyploidy?

Answer 27

Combining of chromosomes of two different species

Question 28

When do autopolyploidy individuals arise?

Answer 28

When cells that are normally diploid (for example), accidentally duplicate their chromosomes, resulting in a tetraploid individual

Question 29

Why are autopolyploidy individuals reproductively isolated?

Answer 29

Their hybrid offspring are triploid and are usually sterile, they cannot produce viable gametes because their chromosomes do not synapse correctly during meiosis

Question 30

Autopolyploidy individuals are reproductively isolated. Under what circumstances can they reproduce viable offspring?

Answer 30

Self-fertilization

Mating with another tetraploid individual

Question 31

Why is polyploidy an exception to the general rule that speciation is a gradual process?

Answer 31

It can result in complete reproductive isolation in just two generations

Question 32

When does allopolyploidy occur?

Answer 32

When individuals of two different but closely related species interbreed- or ‘hybridise’.

Question 33

Why are allopolyploids usually fertile?

Answer 33

Each chromosome has a nearly identical partner with which to pair during meiosis

Question 34

In what organisms is polyploidy important?

Answer 34

Plants- 70% flowering plants and 90% ferns are polyploids- mostly due to hybridization followed by self fertilization, or fertilisation by sibling plants

Question 35

What three species of Tragopogon (salsifies) were introduced to North America in the early 20th century?

Answer 35

T. porrifolous
T. pratensis
T. dubius

Question 36

What species of Tragopogon are tetraploid hybrids?

Answer 36

T. mirus, T. miscellus
First discovered in 1950
Now more widespread then their parents
Studies show these species formed independently 12 times and 21 times respectively.