Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ENVR 202 > L10 - Diversification: Origin of Species > Flashcards

L10 - Diversification: Origin of Species Flashcards

1
Q

Define species?

A
  • The most specific unit of taxonomic classification (domain; kingdom; phylum; class; order; family; genus; species)
  • Also, a biological classification
    • Classifying individuals based on a set of characters
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define gene flow?

A

Movement of new alleles (variants) of a gene from one population to another.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define speciation?

A
  • Creation of new species
  • Dependent on limited or absent gene flow between populations
  • If gene flow does occur between populations, both populations will remain genetically similar
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the mechanisms of speciation?

A
  • Change in gene flow
  • Mutation
  • Genetic drift
  • Natural selection
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What factors might cause a population to separate?

A
  • Geographic or physical barriers (mountains, rivers and deserts that can be newly formed) reduce/eliminate gene flow between populations
    ALSO
  • Different courtship behaviours (mating rituals)
  • Different breeding seasons
  • Different period of activity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What processes might contribute to changes in allele frequency?

A
  • Natural selection
  • Genetic drift
  • Mutation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where does the variation that natural selection acts upon come from?

A

Chance mutations: random change that happens when DNA is replicated that express new traits in an organism.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is Genetic Drift?

A
  • Frequency of genes in a population can change over time, even when not under strong selective pressure
    • Random inheritance can shift gene frequency
    • Likely to occur in small populations, by chance
    • Whole alleles (traits) may even be lost :(
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What will happen to these isolated populations when they come back into contact? Are the different species now?

A
  • Depends on how you define “species”
    • Morphological
    • Biological
    • Phylogenetic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Morphological species concept

A
  • Things that have a similar physical appearance/internal anatomy (size, shape function) are likely to be of same species
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Pros & Cons to Morphological species concept

A
  • LIMITATIONS:
    • Oldest method of defining species
    • Doesn’t take modern genetics into account
    • Not very accurate
  • ADVANTAGES
    • Good for examining the fossil record
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Biological species concept

A
  • Defines a species as members of populations that actually or potentially interbreed (mate with each other) in nature and produce offspring that are fertile (can also reproduce)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Pros & Cons to Biological species concept

A
  • Not all species reproduce sexually
  • Not a practical method (nor ethical): can’t test the ability to mate between every pair of species
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Phylogenetic species concept

A
  • Species are groups of individuals that share a unique common ancestor
  • Determined by showing that individuals share traits (previously morphological, now genetically) unique to that species
    • Causes them to cluster distinctly and form other groups
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why do we care how many species of [ X ] there are?

A
  • Important for conservation discussions
    • The more distantly related these species are, the greater the pool of genetic diversity
    • If we define them as entire species, we look at losing an entire pool of genetic information
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How/why can gene flow be halted between populations? How do populations become new species?

A
  • Allopatry: species in geographic location
  • Parapatry: species with ranges directly adjacent to each other, ranges overlap slightly
  • Sympatry: species existing in the same geographic location
17
Q

What is allopatric speciation?

A
  • Speciation caused by the GEOGRAPHIC ISOLATION of two different populations
  • Low gene flow can occur between populations but must be rare
  • Geographic barrier depends on the type of organism (river, mountain, desert)
    • Theory believed to explain the greatest number of species
    • Believed to be the primary form of speciation that occurs on islands
18
Q

An example of allopatric speciation

A
  • Break up of the Pangea
    • Speciation increases after super continent division
    • Limited to no gene flow, speciation can occur
      Islands
19
Q

What is parapatric speciation?

A
  • Ranges of two speciating populations are actually overlapping, but GENE FLOW IS REDUCED
  • A contentious theory: not all evolutionary biologists believe that parapatric speciation can occur
20
Q

Parapatric Speciation

A
  • Speciation occurs when the ranges of two speciating populations are actually overlapping, but gene flow is reduced
  • A contentious theory: not all evolutionary biologists believe that parapatric speciation can occur
21
Q

How might Parapatric Speciation occur?

A
  • New niche opens
    • Population moves into new niche
    • Niche causes evolution in the new populations
    • Eventually, enough difference to speciate
  • Large range in habitat = increased environmental differences = evolutionary differences
    • Populations at far edges become very distinct
    • Individuals in hybrid zone either disappear or become one of the two distinct populations
22
Q

What happens in the hybrid zone during parapatric speciation?

A
  • Cannot be steady gene flow, or new species will hybridize out of existence
  • Hybrids will be less fit for either habitat
23
Q

Example of parapatric speciation

A
  • Phragmites australis: plant that lives over a very large geographic range
    • In Siberia: it flowers after 1 month of growth
    • In Mediterranean: flowers after 8 months of growth
      • Differences in flowering timing prevents gene flow between populations
24
Q

Sympatric speciation

A
  • A species arises from within a range overlapping with its origin species
  • Also controversial
  • How is gene flow restricted to a sub-population from within a larger population?
  • Cues that animals use to decide who they want to mate with?
    • Chemical signals
    • Communication signals (bird songs)
    • Sexual compatibility
    • Mutations in physical appearance (pigmentation)
25
Q

Sympatric speciation

A
  • A species arises from within a range overlapping with its origin species
  • ALSO CONTROVERSIAL
  • Cues that animals use to decide who they want to mate with?
26
Q

How is gene flow restricted to a sub-population from within a larger population?

A
  • Reproductive Isolation
    • Incompatible reproductive methods reduce gene flow in even completely overlapping populations
      • Different courtship rituals (birdsongs)
      • Different reproductive structures
      • chromosome duplications in plants
      • often arise from mutations
      • infertile hybrid offspring
27
Q

What is a hybrid?

A
  • Organisms that we consider to be different species can interbreed
  • Offspring are often sterile
  • Hybridization is fairly common among plants
28
Q

What is hybrid speciation?

A
  • Some interbreeding can create viable offspring which can survive and mature
  • Why we have some Neanderthal DNA
  • Hybrids between polar bears and grizzly bears that can produce viable offspring
29
Q

Why don’t we see more hybrids in the wild?

A
  • Ranges do not overlap, do not come into contact with each other
    • Changing for polar bears and grizzlies - climate change
  • May have different courtship rituals
  • Some of the traits of each parent will not be advantageous in the environment (brown polar bears would not be successful in the arctic)
30
Q

What is despeciation?

A
  • When two species become one
    • HYBRIDIZATION can cause distinct lineages to collapse into a single lineage with an admixed mosaic genome
    • RARE but there are a few examples: stickleback fish
31
Q

Which mode of speciation?

A
  • Do the ranges of species overlap?
  • Is the entire range of one of the species found within the other?
  • Are sexual practices compatible?
  • Are two species becoming one instead of one species becoming two?
32
Q

What is the primary requirement for speciation to occur?

A
  • Minimal to no gene flow between two populations
  • If populations begin to interbreed, they will lose their distinctness and become one species

ENVR 202 (22 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions