IB Biology Definitions

Bones

Provide a firm anchorage for muscles. They also act as levers changing the size or direction of forces generated by muscles.

Muscles

Provide the force needed for muscle contraction.

Nerves

Co-ordinates muscle contraction so that it is stimulated to contract at precise
times.

Diffusion

The passive movement of particles from a region of high concentration to a region of low concentration.

Osmosis

The passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration.

Denaturation

A structural change in a protein that results in the loss (usually permanent) of its biological properties.

Cell respiration

The release of energy in the form of ATP from the controlled breakdown of organic compounds within the cell.

Gene

A heritable factor that controls a specific characteristic.

Allele

One specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene.

Gene Mutation

A change in the sequence of base pairs found on a DNA molecule.

Homologous Chromosomes

Chromosomes that each have a corresponding chromosome from the opposite-sex parent. A pair of chromosomes with the same genes but not necessarily the same alleles of those genes

Genotype

The alleles of an organism.

Phenotype

The characteristics of an organism.

Dominant allele

An allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state.

Recessive allele

An allele that only has an effect on the phenotype when present in the homozygous state.

Codominant alleles

Pairs of alleles that both affect the phenotype when present in a heterozygote.

Locus

The particular position of a gene on homologous chromosomes.

Homozygous

Having two identical alleles of a gene.

Heterozygous

Having two different alleles of a gene.

Carrier

An individual that has a recessive allele of a gene.

Test cross

Testing a suspected heterozygote by crossing it with a known homozygous recessive.

Sex linkage

When genes are found on one of the two types of sex chromosomes.

Clone

A group of genetically identical organisms or a group of cells derived from a single parent cell.

Species

A group of organisms that can interbreed and produce fertile offspring.

Habitat

The environment in which a species normally lives or the location of a living organism.

Population

A group of organisms of the same species who live in the same area at the same time.

Community

A group of populations living and interacting with each other in an area.

Ecosystem

A community and its abiotic environment.

Ecology

The study of relationships between living organisms and between organisms and their environment.

Autotroph

An organism that synthesizes its organic molecules from simple inorganic substances.

Heterotroph

An organism that obtains organic molecules from other organisms.

Consumer

An organism that ingests other organic matter that is living or recently killed.

Detritivore

An organism that ingests non-living organic matter.

Saprotroph

An organism that lives on or in non- living organic matter, secreting digestive enzymes into it and absorbing the products of digestion.

Trophic level

Step in the movement of energy through an ecosystem; an organism's feeding status in an ecosystem.

Evolution

the cumulative change in the heritable characteristics of a population.

Pathogen

An organism or virus that causes a disease.

Resting potential

The electrical potential across the plasma membrane of a neuron that is not conducting an electrical impulse.

Action potential

The reversal and restoration of the electrical potential across the plasma membrane of a neuron as an electrical impulse passes along it

Transpiration

The loss of water vapour from the leaves and stems of plants.

Linkage group

all those genes on a particular chromosome.

Polygenic Inheritance

the transmission of a characteristic that is influenced by several genes.

Active immunity

Immunity due to the production of antibodies by the organism itself after the body's defence mechanism have been stimulated by antigens.

Passive Immunity

Immunity due to the acquisition of antibodies from another organism in which active immunity has been stimulated, including via the placenta or by injection of antibodies.

Excretion

The removal from the body of the waste products of metabolic pathways.

Osmoregulation

The control of the water balance of the blood, tissue or cytoplasm of a living organism.

Biomass

the total mass of dry organic matter in an ecosystem

Biomagnification

a process in which chemical substances become more concentrated at each trophic level.

Partial pressure

The pressure exerted by a particular gas in a mixture of gases.

Biological control

using a predator or parasite to control a pest species

a high vlue of D in Simpson's Index suggests...

a stable/well-established/ancient ecosystem

when asked to 'outline the use of simposons deiveristy index in...' always start with...

simpsons index is a measure of the species richness of an ecosystem. the higher the index the greater the diversity

ecological succession

a series of changes to an ecosystme, caused by complex interactions between the community of living organisms and the abiotic environment. eventually results in a climax community

in situ conservation

conservation carried out in the organism's natural habitat

characteristics of r strategists

small body size, short life span, early maturity, investing more resources into producing more offspring, reproducing only once

characteristics of K strategists

long life span, late maturity, producing few offspring, reproducing more than once, investing more resources into development

example of organism that switched strategies

Drosophilia

example of r strategist

lemming, Lemmus lemmus

example of k strategist

lion, Pathera leo

abiotic factors affecting plant distribution

temperature, rainfall, light, soil pH, mineral nutrients, salinity

factors affecting distribution of animal species

food supply, temperature, breeding sites, territory, water

explanation of food source as factor affecting distribution of animal species

many animals have specialist requirements e.g. hummingbirds are specialist nectar feeders

explanation of breeding sites as factor affecting distribution of animal species

many animals have specialist requirements e.g. low-eared bats need caves. loss of breeding sites can lead to extinction

explanation of territory as factor affecting distribution of animal species

some animals have specialist territory requirements for obtaining food and breeding e.g. tigers. insufficient territory can lead to extinction

explanation of water as factor affecting distribution of animal species

water may be needed as a permanent habitat e.g. fish or for breeding e.g. amphibians. some animals are specialised to live in very dry areas e.g. bactrian camel.

definition: competition

when two or more species compete for a paricular resource

definition: predation

a predator killing its prey

definition: mutualism

a relationship between two different species where both species benefit from the relationship

definition: parasitism

a relationship between two different species where one species benefits and the other is harmed

example: mutualism

The clownfish Amphiprion percula and sea anemone Heteractis magnifica. Sea anemone provides shelter and protection with its sting for the clownfish. Clownfish draws in other fish that the sea anemone can sting and digest.

example: parasitism

The fish Encheliophis vermicularis lives inside the sea cucumber Bohadschia argus and comsumes its gonads.

Fundamental niche

The potential mode of existence of a species, given its adaptations of the species.

Realised niche

The actual mode of existence of a species, which results from its adaptations and competition with other species.

characteristics brysophyta

mosses and such like - no roots or cuticle, spores produced in capsules

characteristics filicinephyta

ferns - roots, leaves in fronds, cuticle on leaves, not woody, spores produced in structures called sporangia

characteristics coniferophyta

conifers - roots, stems, leaves, woody stems, produce seeds

characteristics angiospermophyta

flowering plants - can from woody tissue, produce seeds

characteristics porifera

sponges - lack tissues and organs, no special shape

characteristics cnidaria

jellyfish and sea anenomes - two forms medusa and polyp, radial symmetry

characteristics platyhelminthes

flatworms- bilaterally symmetric, mouth but no anus, rudimentrary head

characteristics annelida

sedmented worms - segmented body, bilaterally symmetric, mouth and anus

characteristics mollusca

snails, slugs etc

characteristcs arthropoda

bilaterally symmetric, hard exoskeleton, segmented

example of competitive inhibition

disulfiram inhibitor, acetaldehyde substrate, aldehyde dehydrogenase enzyme

example of non-competitive inhibition

nerve gas Sarin inhibitor, acetylcholine substrate, acetylcholinesterase enzyme

example of allostery

enzyme phosphorylase used to remove one glucose phosphate from glycogen for glycolysis, which produces ATP. When there is abundance of ATP e.g. during rest, there is no need for more atp. when there is abundance of AMP e.g. during exercise, there is need

two examples of food chain

phytoplankton --> copepod --> herring --> tuna;

genome

the whole of the genetic information of an organism