Download
1 / 7
70 likes | 79 Views
Exploring the concept of species, their definition, and the factors that contribute to their evolution, including reproductive isolation, genetic drift, gene flow, mutation, nonrandom mating, and natural selection. Discusses allopatric and sympatric speciation, as well as adaptive radiation.
E N D
How do we get new species? A. What is a species? 1. From Latin word for “kind” or “appearance” 2. There are different concepts for which species is defined. The most accepted is the “biological species concept” a. a species is a population or group of populations whose members have the potential to interbreed (mate) in nature and produce fertile offspring.
3. Reproductive isolation – the existence of biological barriers that do not allow two species to produce viable, fertile, offspring. Prezygotic barriers – can’t mate or fertilization can’t happen a. Habitat isolation – rarely encounter one another b. Temporal isolation – breed at different times c. Behavioral isolation – courtship rituals not understood d. Mechanical isolation – mating occurs, but structurally they don’t “fit” e. Gametic isolation – sperm does not recognize egg or can’t survive in other species environment Postzygotic barriers – hybrid can’t develop into viable, fertile adult a. Reduced hybrid viability – development incomplete b. Reduced hybrid fertility – hybrid is sterile c. Hybrid breakdown – offspring weak or not viable
B. Causes for a population to evolve 1. Genetic drift = change in gene pool of a small population due to chance. a. Bottleneck effect = genetic drift resulting from an event that drastically reduces population size b. Founder effect = random change in the gene pool that occurs in a small colony of a population Example: “Founding population” of an island
2. Gene flow = gain or loss of alleles from a population by the movement of individuals or gametes a. migration of individuals into (immigration) or out of (emigration) an area. b. plant pollen 3. Mutation = random change in an organism’s DNA that creates a new allele a. raw material for evolution 4. Nonrandom mating = selecting mates (“sexual selection”) rather than by chance 5. Natural Selection = differential success in reproduction
C. Speciation can take place with or without geographic separation 1. Allopatric Speciation – “Allo”= other; “patra”= homeland a. gene flow is interrupted when a population is divided into geographically isolated subpopulations. b. population can be divided by river, mountains, lake water may decrease causing two lakes
2. Sympatric Speciation – “Same Country” a. How can reproductive barriers between populations evolve when the members remain in contact with each other? b. Switching habitat, food source, or other resource not used by the parent population c. When two species interbreed and produce a hybrid that goes through asexual reproduction which can lead to mutations that make them fertile with other hybrids and not the parent.
D. Adaptive Radiation – the evolution of many diversely adapted species from a common ancestor. 1. Ancestor was introduced to various new environmental opportunities and challenges. 2. Natural Selection caused different traits to be selected for based on environment and challenges ancestor faced.
