Chapter 24 The origin of species Flashcards
SPECIATION
The process by which one species splits into 2 or more species
MICROEVOLUTION
Changes of allele frequency in a population
MACROEVOLUTION
The broad pattern of evolution above the species level.
Eg. Is the origin of new groups of organisms through a series of speciation events
4 for mechanisms of Microevolution
.Mutation
.Natural Selection
. Genetic Drift
.Gene Flow
Why was Darwin fascinated with Speciation
. Because it is responsible for the diversity of life
.It explains the difference between species
. “ “ “ “””””””” the similarities ( as from a common ancestor the unity of life)
SPECIES
THE BIOLOGICAL SPECIES CONCEPT: It is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring- but not produce viable, fertile offspring with members of other such groups.
. thus the members of biological species are united ( are define in terms of )by being reproductively compatible
Scientists have proposed more than two dozen ways to define species. One commonly used definition, called the biological species concept, holds that populations belong to the same species if they can contribute genes to a common gene pool. Reproductive barriers block gene flow between different species. Gene flow between populations tends to hold the gene pool of a species together.
GENE FLOW
The transfer of alleles between populations.
it typically occurs between the different populations of a species
POPULATIONS
A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring
REPRODUCTIVE ISOLATION
Because biological species are defined in terms of reproductive compatibility, The formation of new species hinges on reproduction isolation.
. it is The existence of biological factors ( barriers) that impede members of two species from interbreeding and producing viable ( able to live after birth), fertile offspring.
… Such barriers block geneflow between species and limit the formation of hybrids
Genetic isolation
HYBRIDS
Offsprings that result from an interspecific mating
How are barriers classified
according to whether they contribute to reproductive isolation before or after fertilization
.PREZYGOTIC BARRIERS
.POSTZYGOTIC BARRIERS
.PREZYGOTIC BARRIERS
. Block fertilization from occurring
3 ways .PREZYGOTIC BARRIERS Block fertilization from occurring
- by impeding members of different species from attempting to mate
. To prevent an attempting mating from being completely successful
. hindering fertilization if mating is successful
5 types of .PREZYGOTIC BARRIERS
- Habitat Isolation ( 2 species that occury differet habitats may encounter each other rarely
- Temporal isolation
How does speciation occur
By the evolution of reproductive isolation
Morphological species Concept
Characterizes a species by shape and other structural features
ECOLOGICAL SPECIES CONCEPT
views a species in terms of its ecological niche, the sum of how members of the species interact with non living and living parts of their environment. Emphasizes disruptive selection, as organisms adapt to their environment
PHYLOGENIC SPECIES CONCEPT
Defines a species as the smallest group of individuals that share a common ancestor forming one branch on the tree of life. This is done by comparing characteristics such as morphology molecular sequences with those of other organisms
The five types of pre-zygotic barriers are
habitat isolation Temporal isolation Behavioral isolation Mechanical isolation Gametic isolation
Habitat isolation
Two species that occupy different habitats within the same area may encounter each other rarely if at all even though they’re not isolated by obvious physical barriers such as Mountain ranges
Temporal isolation
Species that breed during different times of the day different seasons or different years cannot mix their gametes
Behavioral isolation
Courtship rituals enable mate recognition - a way to identify potential mates of the same species. Different behavioral rituals will act as a reproduction barrier
Mechanical isolation
Mating is attempted but morphological differences prevent its successful completion
Gametic isolation
Sperm of one species may not be able to fertilize the eggs of another species
Three types off post zygotic barriers.
Reduced hybrid viability
Reduced hybrid fertility
Hybrid breakdown
The genes of different parent species may interact in ways that impair the hybrids development of survival in its environment
Reduced hybrid viability
Reduced hybrid fertility
Even if hybrids are vigorous they may be sterile.
Hybrid breakdown
Envelope if first generation hybrids are fertile and vigorous. their offspring of next generation may be feeble or sterile.
2 ways that speciation can occur
. Allopatric speciation
.Sympatric speciation
ALLOPATRIC SPECIATION
(Other country)
Gene flow is interrupted when a population is divided into geographically isolated subpopulation. It can occur without geographical remodeling. Eg. When individuals colonize a remote area and their descendants become geographically isolated from the parent population.
SYMPATRIC SPECIATION
Occurs in populations that live in the same geographic area
3 means of Sympatric speciation where gene flow is reduced
.polyploidy
.habitat differentiation
.sexual selection
Polyploidy
A species may originate from accident during cell division that results in extra sets of chromosomes . More common in plants
2 distinct forms of polyploidy
Auto polyploid
Allopolyploid
Auto polyploid
An individual that has more than 2 chromosome sets that are derived from a single species. 2n to 4 n
