Lecture 20 Flashcards
What is Microevolution?
changes in allele frequencies in a
population (with in the same species)
What is Macroevolution?
Evolutionary change above the species level
What does this include?
Includes the origin of a new group of organisms (speciation) or the cumulative evolutionary change over a long period
What is Speciation?
the process by which one species splits into
2 or more species, i.e. new species
What is Evolutionary theory?
Must explain how new species originate in addition to how populations evolve
What has traditionally been used to distinguish species?
Morphological differences.
What does the biological species concept emphasize?
emphasizes reproductive isolation
How is a population or group of populations defined according to the biological species concept?
As a group whose members can potentially breed with each other to produce viable, fertile offspring.
What distinguishes this group from others according to the biological species concept?
They CANNOT produce viable, fertile offspring with members of other species.
What are isolating mechanisms?
they are biological factors that impede members of two species from producing viable, fertile hybrids.
What do isolating mechanisms do?
They preserve genetic integrity
How do they preserve genetic integrity? By preventing WHAT?
by preventing gene flow between species
What do prezygotic barriers impede or hinder?
impede mating between species or HINDER fertilization if members of different species attempt to mate
What do prezygotic barriers ensure?
They ensure that a zygote is never produced
How many types of prezygotic barriers are there?
5
What do postzygotic barriers prevent?
often prevent the hybrid zygote from developing into a viable, fertile adult
complete the sentence: This means that while a zygote is produced…..
the resulting hybrid cannot reproduce itself once mature
How many types of postzygotic barriers exist?
3 types
For Prezygotic Barriers, name an example of habitat isolation
Aquatic vs Terrestrial
For Prezygotic Barriers, name an example of temporal isolation
Breed at different times of the year
Name an example of behavioral isolation
For Prezygotic Barriers, the female will only mate with a male with a certain courtship ritual
For Prezygotic Barriers, name an example of mechanical isolation (2)
-Shells spiral in different directions
-Genital openings not aligned
For Prezygotic Barriers, name an example of gametic isolation
Sperm will not fertilize the egg of another species (i.e. unable to survive, cannot penetrate egg…)
What are the 3 types of Postzygotic Barriers?
- Reduced Hybrid Viability
- Reduced Hybrid Fertility
- Hybrid Breakdown
When you think of Prezygotic Barriers, what should you immediately think of?
Prezygotic Barriers -> impede fertilization
When you think of Postzygotic Barriers, what should you immediately think of?
Postzygotic Barriers -> impede hybrid offspring
The biological species concept cannot be applied to 2 types of organisms, which ones?
- Asexual organisms
- Organisms about which little is known regarding their reproduction (ex. Fossils)
What are 2 other definitions of Species?
1) The morphological species concept
2) The ecological species concept
3) The phylogenetic species concept
What is the main idea of The morphological species concept?
Characterizes a species in terms of its body shape, size, and other structural features
What is the main idea of The ecological species concept?
Views a species in terms of its ecological NICHE
What is the main idea of The phylogenetic species concept?
trace the phylogenetic history of organisms (comparing morphology & molecular sequences)
Speciation can occur in two ways, name them:
1) Allopatric speciation
2) Sympatric speciation
Which one is related to the geographic separation of populations?
Allopatric speciation
What does the geographic separation of populations restrict?
gene flow
When does Sympatric speciation occur?
occurs in geographically overlapping
populations
Sympatric speciation is when biological factors reduce gene flow, give 2 examples of these biological factors
- chromosomal changes
- non-random mating
Let’s talk about Allopatric speciation: What are examples of geographic barriers that cause separation?
Mountain ranges, glaciers, land bridges, lakes splitting, and island colonization.
The significance of the barrier depends on what?
on the ability of organisms to move about
How do gene pools diverge (move about) in allopatric speciation?
Due to different selective pressures, mutations, and genetic drift (bottleneck and founder effects).
Define allopatric speciation.
It’s when separated populations evolve differences preventing interbreeding and fertile offspring production.
What is sympatric speciation?
when speciation occurs in populations that OVERLAP geographically.
This overlap means that populations of species occupy the same WHAT?
the same RANGE
What are the 2 ways Sympatric Speciation can occur?
- A change in *ploidy (plants)
– A change in ecology (animals)
How does change occur in ecology for animals (2)?
habitat & sexual selection
What is polyploidy?
the presence of extra sets of chromosomes
(more than diploid number)
How does polyploidy happen in cells?
due to accidents during cell division
How has polyploidy influenced evolution?
It has caused the evolution of some plant species.
In Sympatric Speciation, what is an AUTOpolyploid?
an individual that has more than two chromosome sets, all derived from a single (SAME) species
What happens during cells division to get an autopolyploid?
failure of cell division = tetraploid branch
gametes produced are diploid
offspring = viable & fertile (a new biological species)
What is an ALLOpolyploid?
a species with multiple sets of chromosomes derived from DIFFERENT species
How can a sterile hybrid become fertile in subsequent generations?
Various mechanisms may transform a sterile hybrid into a fertile polyploid over time.
Are polyploid hybrids fertile with each other?
Yes (can produce fertile offspring among themselves)
Can polyploid hybrids breed with either parent species?
no
What is an example of a change in ecology affecting speciation?
The North American maggot fly (Rhagoletis pomonella)
What was the original habitat of the North American maggot fly?
Native hawthorn trees
What happened about 200 years ago regarding the habitat of some maggot fly populations?
Some populations colonized newly introduced apple trees
How has the change in habitat affected the maggot fly populations?
Flies feeding on apples have been selected for more rapid development due to the faster maturation of apples compared to hawthorn fruit.
What is the consequence of this difference in development rates?
B/c apples mature more quickly than hawthorn fruit, they don’t develop or mature at the same rate or time
(apple-feeding flies more rapid development)
What does this situation suggest about speciation?
Speciation is underway, as indicated by the temporal isolation between the two groups of maggot flies
Why has Lake Victoria’s cichlid fish population undergone explosive adaptive radiation? (due to what?)
Due to specialization for exploiting different food and other resources.
How old is Lake Victoria, and how many species of cichlid fishes does it house?
The lake is only 12,000 years old but is home to 600 species of cichlid fishes.
What role does sexual selection play in the diversification of cichlid fishes?
Sexual selection = where females choose mates based on APPEARANCE
Sexual selection contributes to what?
it contributes to speciation
How do females select mates among cichlid fishes? (under normal and orange light)
Females have specific COLOR preferences. Under normal light, they choose males of their own species, but under orange light conditions, they may mate with other species.
What reproductive barrier keeps the gene pools of different cichlid species separate?
Mate choice, primarily based on color preferences, acts as the main reproductive barrier.
What are the 2 different models that have been developed to explain the evolution as observed in the fossil record models?
1) Gradualism
2) Puntuated equilibrium
Which one has a continuous evolution over long periods? and which one has an evolution over short periods?
1) Gradualism -> LONG PERIODS
2) Punctuated equilibrium -> SHORT PERIODS
Punctuated equilibrium is triggered by what?
by environmental changes
Why is gradualism over a long period?
Since the fossil record is incomplete, we rarely see all stages of evolution.
How long does speciation occur according to the theory of punctuated equilibrium?
speciation occurs in a relatively short period (Short = 1000s of years!)
What is macroevolution?
refers to evolutionary changes above the species level, where phenotypic differences are so significant that new species are assigned to different taxonomic categories.
Evolutionary Novelties can arise from 2 ways, name them:
1) Gradual refinement
2) Major body changes
Gradual refinement of what?
of existing structures (cumulative change over millions of speciation episodes)
How does the gradual refinement of existing structures contribute to evolution?
natural selection improves structures based on their current utility rather than anticipation of future needs.
What does the fossil record indicate about the evolution of flight?
Light bones predated flight
(suggesting they initially served a different function on the ground, possibly in agile, bipedal dinosaurs)
What was the original function of feathers? (3)
used for courtship, thermoregulation, or camouflage
How did natural selection adapt structures for flight?
Once FLIGHT BECAME ADVANTAGEOUS, natural selection gradually changed structures to be adapted for flight, enhancing their aerodynamic properties.
Major changes in body can result from changes in WHAT (2)? (genes that control what and what)
a) genes that control development
b) genes that control the spatial organization of body parts
For mutation in genes that control development, a change in what (2) has led to many striking evolutionary transformations?
change in the rate or timing of developmental events
Why are the feet of the tree-dwellers relevant to this subject?
The feet of the tree-dwellers are adapted or climbing vertically, with shorter digits and more webbing.
What would be the result if mutations in
regulatory genes switched off foot growth early?
Stunted feet
For mutation in genes that control spacial organization, what role do Hox genes play in animal embryo development?
Hox genes provide POSITIONAL INFORMATION in an animal embryo
The positional information guides cells to develop into what?
to develop into structures appropriate for specific locations
What is one major transition in the evolution of vertebrates?
the development of walking legs in tetrapods from the fins of fishes.
How do mutations in genes controlling spatial organization contribute to evolutionary change?
Mutations in spatial organization genes, such as Hox genes, lead to significant evolutionary changes by altering/reshaping the developmental pathways and resulting structures in an organism’s body plan.
Why is extinction important in evolution?
Extinction creates opportunities for adaptive evolution by opening up empty ecological niches.
How does extinction facilitate evolution?
Extinction creates vacant ecological niches, allowing new species to evolve and fill those spaces.
What are some geological periods?
Name the three major eras:
Paleozoic, Mesozoic, Cenozoic.
List some periods within these eras:
Permian, Triassic, Jurassic, Cretaceous, Tertiary/Quaternary
How did the extinction of dinosaurs affect mammals?
Mammals were able to diversify due to the disappearance of dinosaurs.
Explain the advantages this extinction provided for mammal evolution.
*more food, less competition/risk of predation
What are regional adaptive radiations?
Periods of evolutionary change where groups of organisms form many new species to occupy various ecological roles in a specific area.
Why are regional adaptive radiations significant/important?
They lead to the diversification of species into different ecological niches, exploiting new resources and habitats.
How do regional adaptive radiations occur?
They occur when new ecological opportunities arise
Often due to what are there new ecological opportunities?
often due to geographical isolation, environmental changes, or the extinction of competing species.
Give an example of regional adaptive radiation.
Bird species diversification on islands, where new ecological niches are available due to the absence of certain mainland bird species.
