Speciation

Question 1

Speciation

Answer 1

one species becoming two or more species
Bridges gap between microevolution and macroevolution
Rise of new groups of organisms
Speciation results in differences in 
morphology (structure of organisms)
Physiology
Biochemistry (chemical processes)
DNA sequences

Question 2

Species

Answer 2

Characterized based on differences in body shape and other anatomical structures
Categorized by ecological niche: sum of interactions between a species and the abiotic factors (nonliving) of the environment
Smallest group of organisms (individuals) with a common ancestor
Focuses on reproductive barriers

Question 3

Process of speciation

Answer 3

Isolation of gene pools or two or more populations of a species
Preventing gene flow
Inability to interbreed even if mating is attempted, and if offspring is produced, they are not fertile

Question 4

Pre-zygotic Barrier

Answer 4

if for some reason a sperm from one species does fertilize an egg of another species, get a hybrid

Question 5

Post-zygotic Barrier

Answer 5

result in reproductive isolation of the hybrid

Question 6

Habitat isolation

Answer 6

impedes mating, get reproductive isolation and over time speciation

Question 7

Temporal Isolation

Answer 7

Results in speciation
Breeding at different times of the day
Breeding during different seasons
Breeding during different years
Crickets: 
G. Firmus (left)
Matures later
G. Pennylvanicus
Matures earlier

Question 8

Blue-footed Boobies

Answer 8

Female will not mate with the male unless he does a high-stepping dance that impresses her
Female is looking for mate that will increase her offsprings survival and chance of success
Prevents breeding between different species
Once the male has attracted the female, she has to do the pointing display

Question 9

Mechanical Isolation

Answer 9

genitals of male and female have to fit like a lock and key; if they don’t, sexual activity will not occur. Cannot get passing of sperm to the egg

Question 10

Gametic Isolation

Answer 10

Mating occurs but the gametes do not fuse
Sponges release their egg and sperm into the water, can have many species. Receptor site on the surface of the egg must match the sperm. Only sperm from the same species is going to fertilize the egg

Question 11

Postzygotic Barriers: reduced hybrid viability

Answer 11

Result in reproductive isolation
This occurs after a hybrid is formed
Hybrid = offspring of 2 sub species (closely related species )
Prevent the hybrid from developing into a viable fertile adult
Salamander - genus ensatina, sometimes inbreed, usually hybrid embryo does not complete development
If it does, they don’t last long - decreased viability

Question 12

Post zygotic Barriers: reduced hybrid fertility

Answer 12

Horse has 32 chromosomes per gamete
Donkey has 31 chromosomes per gamete

Not much difference in # of genes that are donated by each parent
Why the hybrid (mule or hinny) is viable, live to be old, but are infertile

Question 13

Post zygotic Barriers: hybrid breakdown

Answer 13

First generation hybrid is viable and fertile due to hybrid breakdown
Mating between hybrids or between hybrid and one of the parents results in hybrid that is weak and infertile
Different strains have accumulated recessive mutant alleles as they have evolved from a common ancestor
Hybrids are plants of the next generation
Have too many recessive mutant alleles

Question 14

Allopatric Speciation

Answer 14

Population is decided by physical barriers into sub-populations
Snapping shrimp
Large population until isthmus of panama formed
Prevented gene flow
Different species on either side of the isthmus
Geographical separation
Can also occur when individuals of a population colonize remote areas
Happened with flightless cormorant
Ancestor was a flying species
Some colonized in Galápagos Islands - no gene flow between colonists and original population - leads to reproductive isolation due to genetic divergence and results in speciation

Question 15

Sympatric Speciation

Answer 15

Speciation can also occur while individuals of a population are in the same location.
Need to have a decrease in gene flow

Question 16

Sympathetic Speciation: polyploidy

Answer 16

More than 1 complete set of chromosomes
Chromosome # is greater than 2n
Reproductively isolated from diploid individuals
4n x 2n = 3n
Can produce fertile offspring
If mate with another tetraploid..produce tetraploid offspring that is fertile
Tetraploid is a new biological species

Question 17

Allopolyploidy

Answer 17

Two different species interbreed to produce hybrid
Produce very few egg and sperm, don’t have any homologous chromosomes
During meiosis to produce egg and sperm, homologous pairs cannot form
Gametes without correct # of chromosomes or the correct combination of chromosomes
Mechanisms that can change a sterile hybrid into a fertile allopolyploidy in subsequent generations
Fertile when mating with each other, new biological species

Question 18

Habitat Differentiation

Answer 18

Occurs when genetic factors allow a sub population to exploit a habitat or resources that are not used by the parent population
N. American maggot fly
Colonized the Hawthorne tree originally
Apple tree was introduced to US 200 years ago-a subpopulation of maggot fly colonized apple tree
Fruit of hawthorn is produced one month later than the fruit of the apple tree
Offset of life cycle - prevents gene flow
Not yet separate species

Question 19

Sexual Selection

Answer 19

Lake Victoria, Africa - 600 species of cichlids
Species originated 100,000 years ago from a few species
1. Sub groups - exploit different food sources led to genetic divergence resulting in reproductive isolation and speciation
2. Sexual selection is another factor - females choose their mate based on male breeding color
Main reproductive barrier, led to decrease is gene flow

Question 20

How long does it take for a new species to form?

Answer 20

Gradualism Model: small constant evolutionary changes that occur over hundreds of thousands of years, leads to speciation
Diagram on left
Punctuated Equilibrium Model: hundreds of thousands of years of no evolutionary change. Followed by rapid evolutionary change
Occurs over a few thousand years
What is the total time between speciation events?
Can be as little as 4,000 years or as long as 40 million years
Lots of variability in time frame

Question 21

How much genetic change must occur to give rise to a new species?

Answer 21

Evolution of reproductive isolation can be the result of a single gene change 
Japanese land snail (on left)
1 gene change reversed the direction of the spiral in the shell
When the spiral is in different directions, the genitalia of the snails are not properly oriented for mating
Mechanical isolation
Hybrid Sunflower (on right)
Took at least 26 chromosomal changes for reproductive isolation and speciation to occur
It can take very few changes in genetic code

Question 22

From speciation to macroevolution

Answer 22

Genetic changes accumulate resulting in speciation occurring over and over again results in differences in organisms that accumulate
Leads to formation of new groups of organisms - dramatically different than their ancestors
Increase in population size
Other groups decrease in size or become extinct
These events lead to large scale of evolutionary change — macroevolution