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envr 202 > lecture 9 + 11 > Flashcards

lecture 9 + 11 Flashcards

1
Q

What are the two ways to distinguish a species?

A
  1. Taxonomic rank.
    - the most specific unit of taxonomic classification.
  2. A biological classification.
    - a way we try to classify individuals based on a set of characteristics.
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2
Q

What is speciation and how does it occur?

A

Speciation is the creation of new species.

It is dependent on a change in gene flow, mutation, genetic drift, and natural selection.

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3
Q

What is gene flow? What happens if it occurs?

A

The movement of alleles (variant) of a gene from one population to another.

If gene flow does occur between populations, they will remain genetically similar - they cannot become different species if they share the same genes.

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4
Q

What are factors that may cause a population to seperate (or stop exchanging genes) ?

A
  1. Geographic or physical barriers.
  2. Different courtship behaviors (e.g. different mating rituals).
  3. different bredding seasons.
  4. Different periods of activity (e.g. diurnal vs nocturnal).
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5
Q

What are the steps to giraffe/species speciation?

A

Step 1: something causes a population to sepearate.

Step 2: mechanisms of change lead to an accumulation of genetic and phenotypic difference.

  • gene flow is mostly absent.
  • natura selection, mutation, and genetic drift affect isolated populations differently.

Step 3: different isolated populations rise from one species.

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6
Q

Where did the variation that natural selection acts on come from?

A

Natural selection can favor different variations in traits between populations that:

  1. Already exist when they seperated.
  2. Newly arose from chance mutations.
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7
Q

What is genetic drift?

A

Based on probability of different genes in a population can change over time, even when not under selective pressure.

  • Likely to occur in small populations, by chance.
  • whole alleles (traits) may be lost, by chance.
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8
Q

Define the morphological species concept.

A

Two populations have distinguishable phenotypic characteristics (e.g. physical appearance, internal anatomy) are classified as different species by this concept.

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9
Q

For which organisms might morpholgical traits be the most useful way of classifying species?

A

Older organisms - we don’t have their DNA, but we have their fossils.

We can examine the fossil record to distiguish species.

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10
Q

What are the limitations to the morphological species concept? What would be a better process?

A
  1. Sorting species by appearance is a very coarse-grained way of differentiating groups.
  2. Does not take modern genetic into account (e.g. how genes and other microevolutionary differences affect what individuals looks like).

It is more accurate to use ecological and molecular evidence to determine whether individuals are the same species.

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11
Q

What is the biological species concept?

A

Defines a species as members of populations that actualy or potentially interbreed (mate with each other) in nature and produce offspring that are fertile (that can also reproduce).

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12
Q

What are the issues with interbreeding in the biological species concept?

A

Assumes sexual production:

  1. Not all species reproduce sexually.
  2. Does not work for asexual species (plants and animals).
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13
Q

What are the limitations with the bioloical species concept?

A

It cannot be use in all scenarios where we would liek to distinguish species.

We can’t (or don’t have to) test the ability to mate between every pair of species.

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14
Q

What is the phylogenetic species concept?

A

Species are groups of individuals that share a unique common ancestor.

It is determined by showing that individuals share traits (e.g. morphological, genetic) unique to that species.

Causes them to cluster distincly from other groups.

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15
Q

What are the 3 ways that populations evolve to become new species?

A
  1. Allopatry.
  2. Parapatry.
  3. Sympatry.
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16
Q

Explain allopatric speciation.

A
  • species in geographic isolation.
  • low gene flow is rare.
  • speciation following the break up of pangea.
  • primary speciation of island habitats (mainland to island colonization).
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17
Q

Explain parapatric speciation.

A
  • species with ranges directly adjacent to each other.
  • population ranges are overlapping
  1. Opening of new niches at the edge of a population.
    - new niches = evolution in the new population = speciation if there enough difference.
  2. The environment differs across a large range.
    - environment difference = evolution differences.
    - population at the far edge become different.
    - individuals in the middle either disappear or become one of the two populations.
  3. No steady gene flow.
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18
Q

Explain sympatric speciation.

A
  • species existing in the same geographical location.

Gene flow is restricted = reproductive isolation.

  • reproduction methods are incompatible.
  • different courtship rituals, reproductive structures.
  • often arise from mutations.
  • infertile hybrid offspring.
  • chromosone duplication in plants = speciation.
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19
Q

Explain the reproductive isolation of birds of paradise.

A
  • High sexual dimorphism between sexes.
  • Extreme female choice.
  • All descended from a common ancestor.
  • Many still can interbreed - only possibel if the female choose a male from another species.
20
Q

What is the difference between creeps and jerks in evolution?

A

Creeps: gradual process over time = gradual speciation.

Jerks: sudden abprut changes = puntuated equilibrium.

21
Q

Explain gradual speciation.

A

Traits change slowly and gradually over time.

Many morphological intermediates (evolutionary steps between ancestral species/trait and a more modern one).

22
Q

What are the isses with gradualism?

A

If intermediate forms are adaptive, why does evolution continue?

Why doesn’t evolution move towards stabilizing selection instead of changing traits over time?

23
Q

Explain the evolution of the eye.

A

Evidence for a gradual evolution: fossils found of intermediate forms of the eye evolution.
- proved that intermediate forms would be able to persist and form species.

24
Q

Explain punctuated equilibrium.

A

Species diverge quickly - after a quick divergence, species remain unchanged over long periods of time.
- Stabilizing selection.

Single (or very few) mutations must occur in a short period of time - must be severe enough to cause noticeable changes in the phenotype, but not so severe that the fitness of the organism is negatively impacted.

Must be reproductive or geographic isolation between he ancestral species and the new species.

25
Q

What are the issues with differentiating gradual speciation vs punctuated equilibirum based on fossil record?

A

May be biased by an incomplete fossil record - missing many intermediate form in the fossil record.

26
Q

Why do some living fossils remain morphologically unchanged while others have rapid morphological changes?

A

No clear answer - maybe because the living fossils live in a stable habitat (e.g. deep sea).

27
Q

What is fitness a function of? what is the relationship between fitness and the environment?

A

Fitness is a function of survival and reproductive success.

Environment interacts with the fitness of an organism.

Fitness = greater contribution to the next generation = evolution.

28
Q

What are mal adaptive traits? Why is it used?

A

A trait which is detrimental to fitness.

Sexual selection - the maladaptive traits may not be beneficial to the survival aspect of fitness, but they impact the reproductive fitness of individuals.

29
Q

What are primary sexual characteristics?

A

Difference in the biological sexes directly related to reproduction (e.g. genitalia).

30
Q

What are secondary sexual characteristics?

A

Traits which are used in sexual selection, but are not required for sexual reproduction.

  • horns, pretty feathers, etc.
  • can be for direct competition, or attractiveness.
31
Q

What are the 2 types of sexual selection?

A
  1. Intrasexual selection: within the same sex.

2. Epigamic (intersexual) selection: between sexes.

32
Q

Explain intrasexual selection. What are the common sexual dimorphimisms?

A

Direct competition between two members of the same sex for the opposite sex.

Polygynous species (one male, many females).

Common sexual dimorphism patterns:

  • larger males than females.
  • males have sexual ornaments used primarily for fighting other males (antlers).
  • similar male/female color.
33
Q

Explain intersexual selection.

A

Selective pressure from the members of one sex having complete choice over a mate of the opposite sex - display or other courtship to attract members of the opposite sex.

Monogamous pairs.

34
Q

What are the common sexual dimorphimisms of intersexual selection?

A
  1. Where the male does not stay to raise the offspring:
    - males are often more colorful than females (extreme sexual ornamentation).
    - females are often larger than males, or similar size.
  2. Where males help raise offspring:
    - both sexes are often the same colour and size.
35
Q

Why is female choice more common for epigamic selection?

A

Males and demales invest different levels of resources into propagating their genes.

Males:

  • sperm: low input, high output.
  • reproductive success = mating with as many females as possible.
  • many mates = the male can afford to select suboptimal mate.

Females:

  • eggs = high energy investment, fixed number.
  • pregnancy = energy intensive.
  • repoductive success = breeding with the BEST male (fit offspring).
  • costly to choose a poor mate.
36
Q

What is Bateman’s Principle?

A

The sex which invests the most in producing offspring will become a limiting resource over which the other sex competes.

  • epigamic and intrasexual selection are types of mate competition.
  • implies the male can be the sex that invests more.
37
Q

What is the Fischerian Runaway Selection Hypothesis?

A
  1. Females prefer a secondary sexual characteristic.
  2. Females select that mate, then passes that secondary character to her male offspring.
  3. She also passes on a genetic trait in her daughters to desire that secondary sexual characteristic.
  4. Creates a positive feedback, increases the desirability and extreme nture of the character over generations.
38
Q

What is the Sexy Son Hypothesis?

A

Females choose attractive mates because it means that their own male offspring will be better able to attract mates.

39
Q

What is the Handicap Hypothesis?

A

Extreme secondary sexual characteristics indicate to the opposite sex that the individual can afford to waste resources on developing the secondary sexual characteristics.

Effectively, the individual can ‘handicap” itself, and yet still survive - therefore, a good choice for a mate.

40
Q

What is coevolution or reciprocal evolution?

A

Where two (or more) species impact each other’s evolution.

41
Q

What is the difference between natural selection and coevolution?

A
  1. Natural selection: broad changes in phenotypes in response to environmental conditions.
    - abiotic (climate).
    - biotic (species interactions).
  2. Coevolution: small number of traits/genes in one species are directly impacting the evolution of a second suite of traits/genes in another species.
42
Q

What is an evolutionary arms race? What are the 2 types?

A

Two species which develop adaptations and counter-adaptations in response to each other.

  1. Symmetrical arms race.
    - selection pressures are identical on two species.
    - two species whose interactions result in them co-evolving the same trait.
  2. Asymmetrical arms race.
    - contrasting selection pressures.
    - both species are co-evolving, but the selection pressure acting on the two species is different.
43
Q

What is symbiosis? What are the 3 types?

A

A close and prolonged interaction between organisms of different species. Can be beneficial to both partners, neutral to one partner, or harmful to one partner.

Parasitism, obligate mutualism, facultative mutualism.

44
Q

What is mutualism and what are the 2 types?

A

Interactions between two different species mutually benefit each other.

  1. Obligate mutualism.
    - two species must co-operate in order for both to survive.
    - the survival of one species depends on the survival of the other.
  2. Facultative mustualism.
    - both species derive benefit from each other, but one would survive if the other went extinct.
45
Q

What is parasitism?

A

Interaction between two different species where one benefits at the expense of the other.

Parasitism relationships are often very finely tned to preserved the life of the host - the parasite needs the host to survive to complete its lifecycle.

envr 202 (15 decks)

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