Human Impact on Evolution

Alleles and variation

  • Created by: Maisie
  • Created on: 08-03-11 14:59

Alleles and variation Definitions




Phenotypic variation

Allele Frequency


Genetic factors

Environmental factors

Selective Advantage

1 of 10

Alleles and variation Definition answers

Mutation-a permanent change in the amount or arrangement ofa cell's DNA   

Allele- An alternate form of DNA     

Phenotypes-The characteristics of an organism resulting from its alleles                   

Phenotypic variation-The total variation in the characteristics of an organism, usually visible, resulting from both its genotype and the effects of the environment.    

Allele Frequency-The number of times an allele occurs within the gene pool    

Parasites- An organism that lives in or on and takes its nourishment from another organism. A parasite cannot live independently           

2 of 10


Genetic factors-factors such as pressence of certain alleles       

Environmental factors- factors of an organim's surroundings and experince's, such as diet and food availability    

Selective Advantage- a variation that gives one organism an advantage over another organism, making it more likely that it will survuve and reproduce.

3 of 10

Selection Definitions

Intraspecic competition

Natural selection

Selective Pressure



4 of 10

How the use of an antibiotic can increase the leve


5 of 10

Selection Definition Answers

Intraspecic competition- competition betweeen organisms of the same species

Natural selection- the process by which the best adapted organisms in a population survive, reproduce and pass on their alleles to their offspring  

 Selective pressure- the environmental force altering the frequency of alleles in a population


6 of 10

Isolation and the formation of new species definit




Reproductive isolation

Gene pool

Georaphical isolation

7 of 10

Isolation and the formation of new species definit

Species- a group of similar organisms which can interbreed to produce fertile offspring

Speciation- the process by which new species develop

Isolated- when organisms are seperated from one another and cannot interbreed

Reproductive isolation- when groups within the population become isolated from one another and cannot interbreed

Gene pool- all the genetic information present within a population at a given time.

Georgaphical isolation- the isolation of populations of a species by a georgraphical barrier,such as a river so they can no longer interbreed.

8 of 10


Allopatric speciation

Sympatric speciation

Prezygotic mechanisms

Postzygotic mechanisms

9 of 10

Allopatric speciation- occurs when populations are prevented from interbreeding because they become geographically isolated

Sympatric speciation- occurs when populations living together become reproductively isolated

Prezygotic mechanisms-reproductive isolating mechanism that takes place before fertilisation

Postzygotic mechanisms- reproductive isolating mechanism that takes effect after fertilisation

10 of 10




i like this !!!! xxxxxxxxxxxxxxxx



Thankyou :) **

Similar Human Biology resources:

See all Human Biology resources »See all DNA, genetics and evolution resources »