The Origin of Species
| Topic Review on "Title": |
What is a species?
There are two concepts about a species: morphological species and biological species. Morpho-species hinges on differences in appearance. Biological species is based on whether or not animals can breed with one another successfully and generate viable fertile offspring. According to morphological species concept, animals belong to same species have similar form, shape and appearance. The advantage of morpho-species concept is its simplicity; the weakness is its ambiguity. Biological species concept generates less ambiguity in classifying species. However, biological species concept is ineffective for organisms that procreate with asexual reproduction; it is also ineffective for extinct organisms, as there is no way to determine if fossilized organisms could mate.
Evolution Relationships and Biodiversity
There are two basic patterns of evolution: anagenesis and cladogenesis. Anagenesis: In terms of the phylogenetic tree, anagenesis is unbranching evolution, which indicates a direct descendant. Cladogenesis is considered to be “Branching Evolution”; one species may be a common ancestor for many other species.
Speciation Event
A key biological event in speciation involves isolation of gene pool of a population. Gene pool is the complete set of genes of all members in a population. Isolating a gene pool means producing barriers for interbreeding. There are two types of barriers, external barriers such as geographical isolation and land-shifting and internal barriers such as changes of intrinsic genetic composition. Internal barriers include wrong places (different habitats), wrong behavior, wrong anatomy, sterile offspring, etc.
Sympatric Speciation
Sympatric speciation is set of speciation events different from allopatric speciation in the following ways: 1) Internal barriers develop first without initial external barriers; 2) Internal barriers lead to instant reproductive isolation which leads to gene pool isolation. This mechanism of reproductive isolation is usually related to meiotic nondisjunction which results in doubling of gametic chromosomes, and therefore polyploidy is generated and hence inability to mate with usual diploid organisms. Most polyploids go extinct before reproducing. This speciation is more common in plants than animals.
|
| Rapid Study Kit for "Title": |
| Flash Movie |
Flash Game |
Flash Card |
| Core Concept Tutorial |
Problem Solving Drill |
Review Cheat Sheet |
 |
 |
 |
|
| "Title" Tutorial Summary : |
Morpho-species hinges on differences in appearance. Biological species is based on whether or not animals can breed with one another successfully and generate viable fertile offspring. All species are related evolutionally, and the relationship can be reflected on a phylogenetic tree. On a phylogenetic tree, anagenesis is unbranching evolution, which indicates a direct descendant, while cladogenesis is considered to be “Branching Evolution”--one species may be a common ancestor for many other species. A key biological event in speciation involves isolation of gene pool of a population. . Gene pool is the complete set of genes of all members in a population. Isolating a gene pool means producing barriers for interbreeding. There are two types of barriers, external barriers and internal barriers. In plants, sympatric speciation can occur.
|
| Tutorial Features: |
- Concept maps for origin of species.
- Graphic presentation of a phylogenetic tree to describe anagenesis and cladogenesis
- Flow-chart to demonstrate speciation via external barriers
- Flow-chart to summarize the speciation events
|
| "Title" Topic List: |
The Species concept
- Morpho-species concept
- Advantage and disadvantage of morpho-species concept
- Definition of biological species concept
- Weakness of biological species concept
Evolutionary Relationship and Biodiversity
- Basic patterns of evolution
- Anagenesis
- Cladogenesis
Speciation Event
- Isolation of gene pool
- External barriers
- Speciation via external barriers
- Internal barriers: types and function
- Summary of speciation events
Sympatric Speciation
|
See all 24 lessons in college chemistry, including concept tutorials, problem drills and cheat sheets:
Teach Yourself Biology Visually in 24 Hours |
