bio definitions

differentiation

the process by which a cell becomes specialised to perform a specific function

tissue

a group of similar cells work together to perform a specific function

diffusion

the net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient

osmosis

movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane

active transport

the process in which energy is used to move particles against the concentration gradient, from lower concentrations to higher concentrations

turgor pressure

the pressure exerted outward on the cell wall due to water in the cell

plasmolysis

the shrinkage of cytoplasm and cell membrane away from the cell wall due to loss of water when a living cell is immersed in solution of lower water potential

enzymes

biological catalyst that alters the rate of chemical reactions and is chemically unchanged at the end of the reaction

digestion

the break down of large molecules into small, soluble, diffusible substances, that is absorbed into the body

denaturation

the change in the three dimensional structure of enzymes, or any soluble proteins, caused by heat or chemicals like acids and alkalis

egestion

the removal of undigested matter from the body

assimilation

the process whereby some of the absorbed food materials are being converted into new protoplasm or used to provide energy

reducing sugar

sugar that produces red precipitate when boiled with benedict’s solution

peristalsis

rhythmic, wave like muscular contractions in the wall of the alimentary canal

arteries

blood vessel that transport blood away from the heart

photosynthesis

the process in which light energy is absorbed by the chlorophyll is transformed into chemical energy which is used to synthesise carbohydrates from water and carbon dioxide and oxygen released in the process

detoxification

the process of converting harmful substances into harmless ones

phagocytosis

engulfing and ingesting foreign particles such as bacteria by the white blood cell to destroy them

thrombosis

blood clot that forms in the artery

translocation

the transport of manufactured food substances such as sugar and amino acids in plants

transpiration pull

suction force caused by transpiration that is the main factor causing water movement up the xylem

transpiration

the loss of water vapour from the arterial parts of the plant, especially through the stomata of the leaves

breathing

the process that brings about exchange of gases between organism and its environment

aerobic respiration

the release of energy by the breakdown of glucose in the presence of oxygen. carbon dioxide and water are released as waste products. aerobic respiration releases a large amount of energy

anaerobic respiration

the release of energy by the breakdown of glucose in the absence of oxygen. anaerobic respiration releases a relatively small amount of energy

oxygen debt

the amount of oxygen required to remove lactic acid

excretion

the removal of metabolic waste products, toxic substances and substances in excess of the body’s requirements

osmoregulation

the control of water potential and solute concentration levels in the blood to maintain a constant water potential in the body

homeostasis

the maintenance of a constant internal environment

negative feedback

the opposite effect of a stimulus brought about a series of self regulative corrective mechanism as a part of homeostasis to restore the original internal condition

neurotransmitter

certain chemicals that transmit nerve impulses across the synapse

synapse

a junction between two neurons

reflex action

an immediate response to a specific stimulus without conscious control

reflex arc

the shortest pathway in which nerve impulses travels from the receptor to the effector in a reflex action

focusing

the adjustment of the lens of the eye so that clear images of the object at different distances are formed on the retina

endocrine gland

ductless glands that secrete hormones into the bloodstream

hormone

chemical substance produced in minute quantities by an endocrine gland. it is transported by the bloodstream to the target organs where it exerts its effects

gametes

a reproductive cell containing haploid number of chromosome

asexual reproduction

the process resulting in the production of genetically identical offspring from one parent, without the fusion of gametes

sexual reproduction

involving the fusion of two nucleis to form a zygote, resulting in the production of genetically dissimilar offspring

pollination

the transfer of pollen grains from the anther to the stigma

self pollination

the transfer of pollen grains from the anther to the stigma of the same flower, or plant

cross pollination

the transfer of pollen grains from the anther to the stigma of a flower in another plant of the same species

fertilisation

the process by which the male gametes fuse with the female gamete to form a zygote

implantation

the embryo sinks in and embed itself in the uterine lining

menstruation

the monthly discharge of blood from the uterus via the vagina

AIDS

acquired immune deficiency syndrome

mitosis

the process by which a nucleus divides to produce two daughter nuclei, each containing the same number of chromosome as the parent

meiosis

the process by which a nucleus divides to produce four non identical daughter nuclei each containing half the original number of chromosome (haploid)

alleles

a different forms of the same gene that codes for the same characteristic

phenotype

external manifestation of the gene appearance of an expressed trait

genotype

the genetic make up of an organism

homologous chromosome

a pair of chromosome that have the exact same sequence of gene loci

mono hybrid

cross involving parents differing in only one traits

dominant traits

a trait that is expressed preferentially over one another

recessive traits

a trait that is preferentially masked

test cross

the genotype of an organism showing the dominant trait can be determined by crossing it with an organism that is homozygous recessive

codominance

both alleles show the effect and neither of them is dominant over the other

artificial selection

a method used by human beings to produce plants with animals with desirable qualities

natural selection

process that ensures that the best adapted organism in a population survive to reproduce and pass on their genes to the next generation

adaptation

any characteristic of an organism that improves its chances of surviving in its environment

mutation

the spontaneous change in gene structure or chromosome, even chromosome number, and may be inheritable

DNA

a molecule containing genetic information in form of nucleotides

gene

segment of DNA containing heredity code for proteins

genetic code

message stored by gene

double helix

two parallel strands twisted around each other

codon

three nitrogenous bases together make up a codon, each codon codes for one acid

chromosome

DNA molecules that are tightly coiled around proteins

genetic engineering

technique used to transfer genes from one organism to another

vector

DNA molecule used to carry the genes from one organism to another

transgenic

when an organism receives a foreign gene

ecology

the study of the relationship between organism and the natural environment

habitat

the place where organism lives

population

a group of organisms of the same species living in a particular habitat

community

all the populations of organisms living and interacting with one another in a particular habitat

ecosystem

a community and its physical or abiotic environment together