Biology continuity Definitions

What is a gene?

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

What is meiosis

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

What is mitosis?

Cell division that generates new cells for growth and repair. The division of one cell into two genetically identical daughter cells

What are alleles?

Different versions of the same gene

What is a genotype?

the genes that an individual has

What is a phenotype?

the effect of the genetype

What are homozygous alleles?

two of the same alleles

What are herterozygous alleles?

a dominant and a ressive allele

What is codominance?

when both alleles contribute to the phenotype

What are examples of mutations?

Down syndrome as well as albinoism

What are sex linked diseases?

Albinism, colour blindness, sickle cell anaemia and haemophilia.

What is continuous variation?

A characteristic that can take any value within a range

What is discontinous variation?

Something you either have or don't example ablity to roll your tongue.

What causes variation?

(1) Genetic variation

(2) Environmental variation

What is genetic variation?

This is the differences between individual genotypes

What are environmental variation?

These are the environmental differences between organisms.

what is natrual selection

process by which individuals with favorable inherited traits are more likely to survive and reproduce

What are the characteristics of natural selection?

(1) Variation

(2) over production

(3); Struggle for existence

(4) Survival of the fittest

(5) Advantageous characters being passed on

(6) Gradual change

Describe a real life event of natural selection?

The peppered moth ( Biston betularia)