Genetics & Evolution

Testes (testis)

Male organs that produce sperm and testosterone.

Scrotum

Sac that holds and protects the testes.

Sperm

Male sex cell (gamete).

Sperm duct (vas deferens)

Tube that carries sperm from the testes.

Prostate gland

Gland that adds fluid to sperm to make semen.

Urethra

Tube that carries urine and semen out of the body.

Penis

Male organ that delivers sperm.

Ovary

Female organ that produces eggs and hormones.

Egg (ovum)

Female sex cell (gamete).

Oviduct (fallopian tube)

Tube that carries the egg from the ovary to the uterus; site of fertilisation.

Uterus (womb)

Organ where the baby develops.

Cervix

The lower, narrow part of the uterus.

Vagina

Birth canal and where sperm enters.

Gametes

Sex cells (sperm and egg).

Fertilisation

Joining of a sperm and an egg to form a zygote.

Zygote

The first cell formed after fertilisation.

Embryo

Early stage of development after the zygote.

Foetus

Later stage of development when the organism looks more human.

Haploid cell

Cell with half the normal number of chromosomes (gametes).

Diploid cell

Cell with the full set of chromosomes (body cells).

Chromosome

Structure made of DNA that carries genes.

DNA

Molecule that carries genetic information (double helix).

Base pairs

Paired bases in DNA (A-T and C-G).

Gene

Section of DNA that codes for a characteristic.

Genome

The complete set of DNA in an organism.

DNA replication

Process of DNA making exact copies of itself.

Mitosis

Cell division that produces two genetically identical cells.

Meiosis

Cell division that produces four genetically different gametes.

Allele

Different version of a gene.

Genotype

The genetic make-up of an organism.

Phenotype

The physical appearance of an organism.

Dominant allele

Allele that is expressed even if only one copy is present.

Recessive allele

Allele that is only expressed if two copies are present.

Homozygous

Having two identical alleles for a gene.

Heterozygous

Having two different alleles for a gene.

Punnett square

Diagram used to predict the outcomes of a genetic cross.

Variation

Differences between individuals.

Discrete variation

Variation that falls into clear categories.

Continuous variation

Variation that shows a range of values.

Mutation

A change in the genetic code.

Mutagen

Something that causes a mutation.

Beneficial mutation

A mutation that gives an advantage.

Harmful mutation

A mutation that causes problems or disease.

Neutral mutation

A mutation that has no effect.

Evolution

Change in a species over many generations.

Natural selection

Process where organisms better suited to their environment survive and reproduce.

Selective breeding

Humans choosing which organisms breed to get desired traits.

Fitness (biological)

How well an organism can survive and reproduce.

Scientific theory

A well-tested explanation supported by evidence.

Common ancestor

An ancestor shared by two or more species.

Speciation

The process by which new species form.

Evolutionary tree

Diagram showing how species are related through common ancestors.