BIO 2- Chapter 24

What is the biological species concept?

It states that a species is a group of populations whose members have the potential to interbreed in nature + produce viable, fertile offspring. They DO NOT breed successfully w/ members of other groups

Reproductive Isolation is?

The existence of biological factors (barriers) that impede two species from producing viable, fertile offspring

Hybrids are?

offspring that result from mating between different species

Reproductive isolation can be classified by 2 factors (Hint: before/after barrier is called what)

1) Prezygotic-before fertilization-barriers 2) Postzygotic-after fertilization- barriers

Prezygotic barriers block fertilization from occurring by: (there are 3 things it does)

1) Impeding different species from attempting to mate

2) Preventing successful completion of mating

3) Hindering fertilization if mating is successful

Habitat isolation is when?

two species rarely encounter each other because they occupy different habitats, even though they are not isolated by PHYSICAL barriers

Temporal isolation is when?

Species that breed at different times of the day, different seasons, or different years cannot mix their gametes

Behavioral isolation is when?

Courtship rituals+ other unique behaviors to a species are effective among barriers

Mechanical isolation is when?

Morphological differences prevent successful completion of mating (ex. snails→ clockwise can not breed w clockwise)

Gametic isolation is when?

Sperm of one species may not be able to fertilize eggs of another species (ex.urchins)

Habitat isolation + Temporal isolation + Behavioral isolation + Mechanical isolation + Gametic isolation are all what type of barriers?

Prezygotic barriers

Reduce hybrid viability + Reduced hybrid fertility + Hybrid breakdown are all what type of barriers?

Postzygotic barriers

Reduced hybrid fertility is when?

Even if hybrids are vigorous/healthy, they may be sterile (not be able to produce offspring)

Reduced hybrid viability is when?

Genes of the different parent species may interact and impair the hybrid’s development or survival in its environment (ex. salamanders)

Hybrid breakdown is when?

Some first-generation hybrids are fertile, but when they mate with each other or with either parent species, offspring of the next generation are feeble or sterile (ex. grasses)

The biological species concept cannot be applied to ___ or ___

Fossils or Asexual organisms (including all prokaryotes)

The biological species concept emphasizes what?

the absence of gene flow

Gene flow can occur between __ or __

Morphologically + ecologically distinct species

Morphological species concept is?

it defines asexual/sexual species by structural features but relies on subjective criteria

Ecological species concept is?

It defines a sexual/asexual species in terms of ecological niche and emphasizes the role of disruptive selection

What is speciation?

When 1 species splits into 2+ species

Speciation can occur as a result of two general processes:

1) Allopatric speciation a) peripatetic speciation

2) Sympatric speciation b) parapatric speciation

Allopatric speciation is when?

gene flow is interrupted or reduced when a population is divided into geographically isolated sub populations

Peripatric speciation is a type of what speciation? (Hint: allo or sym)

A type of allopatric speciation since populations are isolated + prevented from exchanging genes

Peripatric speciation is when?

A new species is formed from an isolated peripheral population

The definition of barrier depends on the ability of what?

The ability of a population to disperse

Separated populations may evolve independent through what 3 things?

1) Mutation

2) Natural selection

3) Genetic drift

Sympatric speciation is?

speciation that occurs in populations that live in the same geographic area

Parapatric speciation is a type of what speciation (Hint: allo or sym?)

It is a type of sympatric speciation

What is parapatric speciation?

It is when two species evolve in continuous, yet spatially SEPARATED habitats + maintain a zone of contact and do not cease the exchange of genes completely

Sympatric speciation can occur if gene flow is reduced by 3 factors. They are:

1) Polyploidy

2) Sexual selection

3) Habitat differentiation

What is polyploidy?

The presence of extra sets of chromosomes due to accidents during cell division+ can produce new biological species in sympatry within a single generation

What is an autopolyploid?

An individual with more than two chromosome sets derived from a single species

____ is much more common in plants than in animals

Polyploidy

What happens to the fertility of the offspring between the mating of polyploids and diploids?

They have reduced fertility

What is an allopolyploid?

Its a species with multiple sets of chromosomes derived from diff species

TRUE/FALSE: Allopolyploids can successfully mate with each other, but cannot interbreed with either parent species

TRUE

Plant geneticists can produce new polyploid species using chemicals that do what?

to induce errors in cell division

Sexual speciation can drive ___ (Hint: sym or allo?)

Sympatric speciation

Sympatric speciation can also result from the appearance of new ____ niches

New ecological niches

What is a hybrid zone?

A region in which members of different species mate and produce hybrids

Where can a hybrid zone occur?

It can occur in a single band where adjacent species meet (ex. two species of toad interbreed in a long and narrow hybrid zone)

Hybrids are the result of mating between species with incomplete or complete reproductive barriers?

Incomplete barriers

Hybrids often have ___ fitness

reduced fitness

What condition must be met when the distribution of hybrid zones become more complex?

Parent species must be found in patches of the same region

3 alternate outcomes happen when hybrids do not become reproductively isolated from their parent species. they are:

1) Reinforcement

2) Fusion

3) Stability

Reinforcement does what to reproductive barriers?

Reinforcement of reproductive barriers happens through strong selection for prezygotic barriers when hybrids are less fit than parent species

Fusion does what to reproductive barriers?

Fusion of reproductive barriers happens when 2 things happen:

1) when hybrids are as fit as their parents→ substantial gene flow happens between species

2) when gene flow is great enough, reproductive barriers weaken→ parent species can fuse into a single species

What happens if there is extensive gene flow from outside the hybrid zone?

It can overwhelm selection for increased reproductive isolation inside the hybrid zone

What is punctuated equilibria?

It describes these periods of apparent stasis punctuated by sudden change

Punctuated model vs Gradual model (what does it look like?)

Punctuated model is a sudden change - Gradual model is gradual change in a species over time

What does a punctuated pattern in the fossil record suggest about speciation?

Speciation can be rapid

Microevolution happens on a ___ scale + __ population

single scale w/ single population

Macroevolution happens on a scale that what

transcends the boundaries of a single species

TRUE/FALSE: Macroevolution and Microevolution do not rely on the same established mechanisms of evolutionary change mutation

FALSE: Evolution at both of these levels relies on the same, established mechanisms of evolutionary change mutation