Habitat: The physical or abiotic part of an ecosystem, i.e. a defined area with specific characteristics where the organisms live, e.g. oak forest, deep sea, sand dune, rocky shore, moorland, hedgerow, garden pond, etc.

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Haemoglobin: A vital protein found in red blood cells, consisting of 4 polypeptide chains with a haem group on each unit. One oxygen molecule will bind to each Haem group for oxygen carriage in the blood. Key function – to pick up oxygen where abundant (lungs), and release it where needed (tissues).

 

Haemophilia: Sex linked genetic disease, faulty allele prevents blood clotting. 

 

Haploid: A cell/organism which contains a single set of chromosomes e.g. eggs & sperm. Shown as n e.g. n = 23 in humans

 

Herbicide: Chemical which inhibits growth of, or kills, plants (weeds).

 

Heterozygous: Possessing two different alleles of a particular gene. Written as Aa or Bb etc

 

Hierarchy: In taxonomy, a layered system of groups within groups, with no overlap.

 

Homologous chromosomes: A pair of chromosomes that have the same genes in the same places (loci) although not always the same alleles. Human have 23 homologous pairs

 

Homozygous: Possessing two alleles the same e.g. AA or aa. Said to be “true breeding”

 

Huntington’s disease: Genetic disease caused by dominant allele that makes a brain-degenerating protein. Does not begin until age 35-40, often after gene has been passed on

 

Hydrostatic Pressure: the pressure of fluid within a vessel, e.g.: blood in an artery has high hydrostatic pressure. Created by the ventricles.