CHAPTER 14 The Origin of Species Chapter Objectives You should be able to 1. Dis
ID: 186090 • Letter: C
Question
CHAPTER 14 The Origin of Species Chapter Objectives You should be able to 1. Distinguish between microevolution and speciation. rn: change ih gehe pool of population from one to another·S: process one spicies spots into Z 2. Compare the definitions, advantages, and disadvantages of the different species concepts. Describe five types of prezygotic barriers and three types of postzygotic barriers that prevent populations of closely related species from interbreeding. 3. 4. Explain how geologic processes can fragment populations and lead to speciation. 5. Explain how reproductive barriers might evolve in isolated populations of organisms 6. Explain how sympatric speciation can occur, noting examples in plants and animals. 7. Explain why polyploidy is important to modern agriculture.
Explanation / Answer
please find the answer of only question no 2 even though it is lenghty but i cover all the points
Compare definitions, advantages, & disadvantages of species concepts
In ecological system there are following types of species concept and they are:-
1. Biological species concept
It was superior by Ernst Mayr in 1942.
Defination
A biological species is a collection of interbreeding or potentially interbreeding organisms that can generate possible offspring
Advantages
This is a species concept based on a mechanism. Either individuals can or cannot produce viable offspring, although failure may be down to individuals.
The issue of potential interbreeding arises when members of populations are separated but are brought into contact in a lab, or by chance mechanisms.
Disadvantages
2. Morphological species concept
Definition
They are the species in terms of measurable anatomical criteria
Individuals do not have to be exactly the same as each other, because there is variation in morphology among most species
Advantages
Morphology can be readily observed, in many cases without handling or harming the organisms. It is relatively easy to communicate with a whole range of people about morpohology
Disadvantages
3.Genetic Species Concept
The genetic species concept can be thought of as the geneticists’ equivalent of the morphospecies concept, but the measure is genetic similarity or distance.
Advantages
Can provide independent evidence for morphological and biological species. For bacteria and small organisms genetic species concepts can be very useful and save a lot of time. With automated sequencing and web databases it is now very quick to analyse DNA. It is also possible to get many samples from one individual.
Disadvantages
This species concept also relies, to some extent, on human judgement of how much difference is enough to constitute separate species. Taking DNA can be invasive and unnerving for an animal, although many field studies can now use discarded hair, feathers, skin and so on for sequencing. Situations can arise where DNA samples get contaminated with the DNA of parasites living on or in an organism. Communicating with non-specialists about DNA taxonomy can also be very difficult
4.Microspecies Concept
This species concept also uses DNA, but covers organisms that reproduce asexually to give rise to exact genetic copies of themselves.
Advantages:
Apparent criteria and useful for microorganisms and some plants.
Disadvantages:
Some organisms may reproduce asexually, but have high mutation rates and are thus not identical copies.
5.Ecological Species Concept
This is used to describe populations that are adapted to certain ecological niches and because of their adaptations will form discrete morphological clusters.
Advantages
Acknowledges the role the environment plays in controlling morphological development.
Disadvantages
Can miss cryptic species. Niches tend to be assumed and are difficult to define completely. Many taxa exploit overlapping resources, or can suddenly switch if a resource becomes scare. This is not a very vigorous species concept.
6 Mate-Recognition Species
This is an interesting species concept that essentially lets the organisms be the guide as to which species they belong to by observing which other individuals they mate with.
Advantages
a male of species x mate with a female of species y, do they produce viable offspring? Also a non-invasive, observational concept. Other qualifiers can be added to this concept to cover what happens after mating
Disadvantage
Not very clear what advantages this species concept has on its own. The biological species concept covers more cases and mechanisms. Like the Biological Species Concept this species concept applies only to sexually reproducing organisms
7.Cladistic Species Concept
The cladistic species concept relies on the possession of certain shared, derived characters (called synapomorphies) among individuals.
Advantages
This is a species concept based on a mechanism. Either individuals can or cannot produce viable offspring, although failure may be down to individuals.
The issue of potential interbreeding arises when members of populations are separated but are brought into contact in a lab, or by chance mechanisms.
Disadvantages
- Several living species have never been observed mating and then those offspring mating and raising viable.
- Fossils certainly can’t mate any longer
- Some living organisms, e.g. bacteria don’t have sex but can swap genetic material among themselves