CHAPTER 4 & 5 Microevolution and Speciation Flashcards
- evolution on a small
scale within a single population - It is the generation-to-generation
change in frequencies of alleles within a
population
MICROEVOLUTION
How to detect microevolution?
Microevolutionary pattern
= a change in gene frequency over time population evolved
- Generation-to-generation
change in frequencies of alleles
within a population.
MICROEVOLUTION
Frequency of alleles in a population stays the same
generation after generation unless acted upon by some outside force
HARDY WEINBERG THEORY
- a group of individuals that actually or potentially interbreed in nature.
- the biggest gene pool possible under natural
conditions
misleading definition
Species
a lineage-splitting event that produces two or more separate species
SPECIATION
Causes of Speciation
Different species are unable to interbreed and produce healthy, fertile offspring due to barriers called mechanisms of reproductive isolation.
2 Barriers:
1.–
2.–
PREZYGOTIC BARRIERS
POSTZYGOTIC BARRIERS
Causes of Speciation
PREZYGOTIC BARRIERS include:
- Geographical Isolation
- Temporal Isolation
- Behavioral Isolation
- Gametic Isolation
- Mechanical Isolation
Causes of Speciation
POSTZYGOTIC BARRIERS include:
- Mixed set of chromosomes
- Unhealthy individual
- Infertility
Causes of Speciation: PREZYGOTIC BARRIERS
- Populations are prevented from
interbreeding by habitat isolation
is a common way for the process of speciation to begin:
Geographical Isolation
rivers change course, mountains rise, continents drift, organisms migrate, and what was once a continuous population is divided into two or more smaller populations
Causes of Speciation: PREZYGOTIC BARRIERS
Populations are prevented from interbreeding by the difference in their mating or reproduction time
Temporal Isolation
Causes of Speciation: PREZYGOTIC BARRIERS
Two species might have different courtship behaviors or mate preferences and thus
find each other “unattractive”
Behavioral Isolation
Causes of Speciation: PREZYGOTIC BARRIERS
Two species might produce egg and sperm cells that can’t combine in fertilization, even if they meet up through mating.
Gametic Isolation
Causes of Speciation: PREZYGOTIC BARRIERS
Two species might have bodies or reproductive
structures that simply don’t fit together.
Mechanical Isolation
Modes of Speciation
- Allopatric - geographical barrier
- Parapatric -
- Sympatric -
- Peripatric -
- geographical barrier
- partial spatial isolation
- genetic polymorphism
- isolation of a population at the periphery
Modes of Speciation
- occurs when a species separates into two separate groups which are isolated from one another
- physical barrier
- Each species develops differently based on the demands of their unique habitat or the genetic
characteristics of the group that are passed on to offspring
Salamanders in California (other move to west from east, separated by river, causes genetic drift, now the population from west cannot mate to those in east)
Allopatric Speciation
Modes of Speciation
- Happens when small groups of individuals
break off from the larger group and form a
new species - Physical barriers
- one group is much smaller than the other and the unique characteristics of the smaller groups are passed on to future generations of the group, making those traits more common among that group and distinguishing it from the others.
Peripatric Speciation
Modes of Speciation
- A species is spread out over a large geographic area.
- Although it is possible for any member of the species to mate with another member, individuals only mate with those in their own geographic region.
- Instead of being separated by a physical barrier, the species are separated by differences in the same environment
Parapatric Speciation
there is a hybrid zone (where they maintain contact)
ex. the Galapagos finches
Modes of Speciation
- occurs when there are no physical barriers
preventing any members of a species from mating with another, and all members are in close proximity to one another. - A new species, perhaps based on a different food source or characteristic, seems to develop spontaneously.
Sympatric Speciation
