Definitions Of Terms

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Adaptation

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The adjustment or changes in behaviour, physiology, and structure of an organism to become more suited to an environment. According to Charles Darwin's theory of evolution by natural selection, organisms that possess heritable traits that enable them to better adapt to their environment compared with other members of their species will be more likely to survive, reproduce, and pass more of their genes on to the next generation.

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Chromosome

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A double stranded DNA molecule that contains a series of specific genes along its length. In most sexually reproducing organisms, chromosomes occur in pairs, with one member of the pair being inherited from each parent.

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DNA

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Deoxyribonucleic acid. A large biological molecule composed of subunits known as nucleotides strung together in long chains. The sequences of these nucleotides contain the information that cells need in order to grow, to divide into daughter cells, and to manufacture new proteins. Changes in DNA result in mutations, which may be beneficial, neutral, or deleterious to the organism. If these changes occur to DNA in sperm or egg cells, they could be passed onto the next generation.

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Evolution

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Evolution consists of changes in the heritable traits of a population of organisms as successive generations replace one another. It is populations of organisms that evolve, not individual organisms.

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Mutation

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A change in the sequence of one or more nucleotides in DNA. Such changes can alter the structure of proteins or the regulation of protein production. In some cases mutations result in the organism possessing these altered traits to have a greater or lesser chance of surviving and reproducing in a given environment than other members of its species.

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Natural selection

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Differential survival and reproduction of organisms as a consequence of the characteristics of the environment.

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Protein

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A large molecule consisting of a chain of smaller molecules called amino acids. The sequence of amino acids and the molecule's three-dimensional structure are coded by the instructions in DNA and determine a protein's specific function in cells or organisms.

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RNA

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Ribonucleic acid. A molecule related to DNA that consists of nucleotide subunits strung together in chains. RNA serves a number of cellular functions, including providing a template for the synthesis of proteins and catalyzing certain biochemical reactions. The structure of RNA is determined by the sequence of nucleotides on DNA.

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Selective breeding

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The intentional breeding of organisms with desirable traits in an attempt to produce offspring with enhanced characteristics or traits that humans consider desirable. This process is also known as "artifical selection" (compare with "natural selection").

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Survival of the fittest

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A term that refers to the survival of only those organisms best able (fittest) to obtain and utilize resources, resulting in the evolution of organisms that are best adapted to the environment. Darwin used metaphorically to describe "natural selection." The phrase was invented by the 19th century philosopher Herbert Spencer It has been misapplied through history to explain and justify social and economic inequities in human populations ("social Darwinism") or as a method for improving the human condition through selective breeding (eugenics). Survival alone is insufficient for evolution - it's reproduction - passing on of genes that really counts. Most modern biologists no longer use this term when describing or discussing natural selection.

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Trait

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A physical or behavioural characteristic of an organism.

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Cross Breeding

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The process of combining in the offspring a desirable feature of one individual with a different desirable feature from another.

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Inbreeding

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[or in-line breeding] The process, related individuals are allowed to mate. This method is not often used in animal breeding, as there can be health issues in the offspring.

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Selective Agents

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...is what chooses the what adaptations are needed by the organisms in order for them to suit the environment

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Genotype

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... refers to the genetic makeup of a cell. For each individual trait (such as hair or eye color), a cell contains instructions on two alleles, which are alternative forms of the gene obtained from the mother and the father. An individual’s genotype refers to the combination of these two alleles, and can be either homozygous (the alleles are the same) or heterozygous (the alleles are different).

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Phenotype

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The ... is the visible or expressed trait, such as hair color. The phenotype depends upon the genotype but can also be influenced by environmental factors.

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Allele

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A specific variation of a gene.

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Gene

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A section of DNA that controls a certain trait.

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Heterozygous

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Having dissimilar alleles that code for the same gene or trait.

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Homozygous

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Having two identical alleles that code for the same trait.

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Homologous

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- 2 matching sets of autosomes (homologous pairs)

- body parts (from animals and humans) derived from a common ancestral form

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Meiosis

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A type of cellular reproduction in which the number of chromosomes are reduced by half through the separation of homologous chromosomes, producing two haploid cells.

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Mitosis

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A process of asexual reproduction in which the cell divides in two producing a replica, with an equal number of chromosomes in each resulting diploid cell.

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Speciation

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This is the process by which one species splits into two or more separate species. Speciation is responsible for the formation of any new species that appear in the fossil record.

1. Variation - there must be variation in the population or speciation cannot occur.

2. Isolation - this means that different groups of the population are prevented by some mechanism from inter-breeding. Isolation prevents gene flow throughout the population, stopping any differences in one population from reaching the other population.

3. Selection - natural selection affects the genotype and causes changes that prevents the groups breeding even if they came back together again some time in the future. (possible changes eg: courtship behaviour, breeding seasons, sterility, chemical barriers...)

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Nucleotides

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Molecules that make up DNA.

- 3 main parts (phosphate group, deoxyribose sugar, one of four nitrogen-rich bases- adenine, thymine, guanine, cytosine)

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Replication

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The process of copying DNA

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Chromosome Number

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In your body, there are 46 chromosomes. Half of which are from your father and half from your mother. The number of chromosomes in your body cells is the diploid number (2N - means 2 sets)

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Haploid

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Haploid cells have half the number of chromosomes (n) as diploid - i.e. a haploid cell contains only one complete set of chromosomes.

Cell Division and Growth: Haploid cells are a result of the process of meiosis, a type of cell division in which diploid cells divide to give rise to haploid germ cells. A haploid cell will merge with another haploid cell at fertilization.

Examples: Cells used in sexual reproduction, sperm and ova (also known as Gametes)

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Diploid

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Diploid cells contain two complete sets (2n) of chromosomes.

Cell Division and Growth: Diploid cells reproduce by mitosis making daughter cells that are exact replicas.

Examples: Skin, blood, muscle cells (also known as somatic cells)

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Autosome

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... is a chromosome that is not a sex chromosome (allosome)

Autosomes appear in pairs whose members have the same form but differ from other pairs in a diploid cell, whereas members of an allosome pair may differ from one another and thereby determine sex.

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Autosomal

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Autosomal dominant is one of several ways that a trait or disorder can be passed don through families.

- refers to any of the chromosomes other than sex-determining chromosomes (i.e. the X and Y) or the genes on these chromosomes

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X-linked

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X-linked inheritance is a mode of inheritance in which a mutation in a gene on the X-chromosome causes the phenotype to be expressed (capital letters)