22: Macroevolution and Speciation Flashcards
Module 4, Lesson 5
What two phenomena must a species concept account for?
- Distinctiveness among species that occur in the same location
- Connections between populations of the same species living in different areas
Species that live in the same geographic location and often use different parts of the habitat are called…
Sympatric
Species that live in different geographic locations, often separated by a physical barrier, are called…
Allopatric
When two different species inhabit the same area but remain distinct, they are…
Sympatric
Sympatric species usually have visible…
Morphological differences
True or false:
Sometimes sympatric species will have differences that are less visible.
True
Populations tend to exhibit geographic…
Variation
True or false:
A species is normally found in a continuous range.
False
When populations of the same species are located in different areas, they often…
Have distinct differences
Distinctly different populations of the same species may be classified as…
Subspecies
In order to be considered the same species, members of different subspecies must be able to…
Produce fertile offspring together
Why do sympatric species remain distinct despite living in the same location?
They only exchange genetic material with members of the same species
In order to remain the same species, geographically distant populations must…
Experience some gene flow
____ occurs when individuals cannot/will not mate with each other, or when they cannot produce fertile offspring.
Reproductive isolation
Reproductive isolation is a critical aspect of…
Speciation
In order for reproductive isolation to occur, ____ must happen.
A disruption in gene flow
List the two main mechanisms of reproductive isolation.
- Pre-zygotic
- Post-zygotic
Pre-zygotic isolation mechanisms are those that…
Prevent a zygote from forming
List the five main mechanisms of pre-zygotic isolation.
- Ecological isolation
- Behavioral isolation
- Temporal isolation
- Mechanical isolation
- Prevention of gamete fusion
Post-zygotic isolation mechanisms are those that…
Impact hybrid zygotes
List the three main mechanisms of post-zygotic isolation.
- Hybrid inviability
- Hybrid infertility
- Hybrid breakdown
____ occurs when species that live in the same area use different areas of the environment, causing them to not interact.
Ecological isolation
The fact that lions and tigers can produce hybrid offspring but rarely do so is due to…
Ecological isolation
____ occurs when differences in courtship/mating rituals prevent different species from accidentally mating.
Behavioral isolation
____ occurs when species do not mate because they have different mating/breeding seasons.
Temporal isolation
True or false:
Species that are temporally isolated may be able to hybridize in a lab.
True
____ occurs when structural differences in reproductive systems prevent mating.
Mechanical isolation
The fact that many flowers have unique structures or pollinators that limit pollen transfer between species is an example of…
Mechanical isolation
____ is an important mechanism for plants and animals that shed gametes directly into water.
Prevention of gamete fusion
True or false:
Only species that use external fertilization can use mechanisms that prevent gamete fusion.
False
Some species that use internal fertilization also have mechanisms that prevent sperm/pollen from fertilizing eggs.
If mating does occur between members of different species, ____ may prevent hybrids from being produced.
Post-zygotic isolating mechanisms
____ occurs when hybrid embryos do not develop properly, causing them to die before or shortly after birth.
Hybrid inviability
____ causes many surviving hybrids to be sterile.
Hybrid infertility
____ occurs when hybrids survive and are fertile, but have much lower fitness than their parents.
Hybrid breakdown
Under the ____, individuals have to be able to produce fertile offspring to be considered members of the same species.
Biological species concept
The biological species concept defined “species” as…
A group of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups.
List five major complications to the biological species concept.
- Sometimes individuals classified as separate species will produce fertile intermediate offspring
- In-depth studies are often required
- Hybridization is common between plant species
- It is difficult to apply to geographically isolated populations
- It does not apply to asexual organisms
Why does the biological species concept often require in-depth studies of closely-related species?
To investigate whether they are interbreeding and producing fertile offspring
It is difficult to classify plants using the biological species concept because…
Hybridization is very common among plants
It is difficult to apply the biological species concept to geographically isolated populations because…
Interbreeding cannot be observed
Why does the biological species concept not apply to asexual organisms?
They do not mate
The utility of the biological species concept is limited to…
Organisms that reproduce sexually
The ____ applies the term “species” only to populations that have been evolving independently of other populations.
Phylogenetic species concept
Under the phylogenetic species concept, species are identified using…
Phylogenetic analysis
____ represent hypotheses of relationships between species based on analysis of shared traits.
Phylogenies
Phylogenies are also called…
“Evolutionary trees”
What two complications of the biological species concept are solved by the phylogenetic species concept?
- Does not require knowledge about the ability of allopatric populations to interbreed
- Can be applied to both sexually- and asexually-reproducing species
List two drawbacks to the phylogenetic species concept.
- It can lead to defining every slightly different population as a new species
- Populations in a species may not be descended from a single ancestor
True or false:
It is relatively simple to define a species, and there is little debate in the scientific community about the criteria used.
False
Isolating mechanisms may be reinforced by…
Selection
Species formation is a ____ process.
Continuous
True or false:
During the process of species formation, two populations may be only partially reproductively isolated.
True
What happens if two different populations are not fully reproductively isolated and begin interbreeding?
Over time, their differences will disappear and speciation will not occur
What happens if two populations are already reproductively isolated by the time they meet?
They will remain separate species
If hybrids are partially sterile, then selection will prioritize alleles that…
Prevent hybridization
True or false:
It can be argued that “selection may favor reproductive isolation”
True
The continual improvement of pre-zygotic isolation mechanisms is called…
Reinforcement
When two populations are ____, they may display similar morphological features.
Geographically isolated
When two populations occur ____, they will often evolve less similar morphology.
Sympatrically
The development of different morphologies is a ____ isolation mechanism.
Pre-zygotic
When two species live sympatrically, pre-zygotic isolation mechanisms will…
Continually improve
____ can counter speciation.
Gene flow
True or false:
Reinforcement always results in speciation.
False
When partially isolated populations meet, some degree of gene flow will occur if…
Any of the hybrids are fertile
____ serve as a conduit for gene flow.
Surviving hybrids
Adaptive changes in mating signals can result from ____ in new environments.
Selective forces
Adaptive changes can eventually result in….
Reproductive isolation
Random changes in allele frequence can cause…
Reproductive isolation
With enough time, any isolated population will diverge due to…
Genetic drift
If divergence leads to traits which cause reproductive isolation, ____ occurs.
Speciation
If geographic changes cause a population to be broken into smaller populations, then…
Gene flow stops and allopatric speciation may occur
When two similar populations evolve into separate species over time due to geographic isolation, ____ occurs.
Allopatric speciation
Sometimes, geographic isolation is an important prerequisite for…
Speciation
Mainland populations of a species show little variation because…
Gene flow is constantly occuring
Isolated island populations show a lot of variation, because…
Gene flow is very limited
____ refers to a group of species that recently evolved from a common ancestor by adapting to different parts of the environment.
Adaptive radiation
Adaptive radiation can lead to…
Diversity
The rapid diversification of cichlid populations in Lake Victoria is an example of…
Adaptive radiation
List the two hypothesis that attempt to explain the relationship between speciation and the evolutionary changes that occur within a species over time.
- Gradualism
- Punctuated equilibrium
True or false:
Gradualism and punctuated equilibrium are mutually exclusive.
False
True or false:
A species may have experienced episodes of both gradualism and punctuated equilibrium over its history.
True
The hypothesis that small changes occur very slowly, accumulating into large changes over thousands and millions of years, is called…
Gradualism
The hypothesis that species experience periods of little to no change interspersed with short bursts of rapid evolution is called…
Punctuated equilibrium
