Secondary 5 Biology

The process by which green plants use light energy to build glucose from carbon dioxide and water, releasing oxygen.

The plant organelle containing chlorophyll, where photosynthesis takes place.

Membrane sacs stacked into grana inside chloroplasts; chlorophyll sits on them and the photochemical reaction happens here.

The photosynthetic pigment on thylakoid membranes; it absorbs red and blue light and reflects green, making leaves look green.

The first stage of photosynthesis: chlorophyll absorbs light and splits water, producing NADPH, ATP and oxygen.

The combining of carbon dioxide with a five-carbon acceptor to make organic matter, occurring in the stroma.

The carbon fixation cycle in the stroma, using ATP and NADPH to reduce carbon dioxide to glucose.

A pore between two guard cells in the leaf epidermis, admitting carbon dioxide and letting oxygen and water vapour out.

The factor among light intensity, carbon dioxide concentration and temperature that sets the ceiling on the rate of photosynthesis.

A segment of DNA that carries genetic information and controls a particular trait.

Different forms of a gene at the same position on a pair of homologous chromosomes, such as the tall and short stem genes.

An allele expressed even in the heterozygote, conventionally written as a capital letter.

An allele expressed only when homozygous, masked by the dominant allele and written as a small letter.

The combination of alleles an individual carries for a trait, such as TT, Tt or tt.

The trait actually shown by an individual, determined by genotype together with the environment.

A genotype with identical alleles (TT or tt); pure-breeding organisms are homozygous.

A genotype with different alleles (such as Tt), showing the dominant trait but capable of passing on the recessive one.

A grid listing each parent's gametes in rows and columns to predict the genotypes and phenotypes of offspring.

The chromosome pair that determines sex: XX in females and XY in males.

The building block of DNA, made of a phosphate, deoxyribose and one nitrogenous base.

The fixed pairing rule between strands: A-T and C-G in DNA, with A-U during transcription.

The structure of DNA: two antiparallel strands twisted around each other like a twisted ladder.

How DNA copies itself: the strands unwind as templates, and each daughter molecule keeps one parental strand.

Making mRNA in the nucleus from one DNA strand as template, with U replacing T.

The single-stranded nucleic acid that carries DNA's instructions from the nucleus to the ribosome.

The ribosome reading mRNA codons and joining amino acids into a polypeptide.

Three adjacent bases on mRNA corresponding to one amino acid — the unit of the genetic code.

A change of base pairs within a gene that can alter a protein's amino acid sequence, as in sickle cell anaemia.

A change in the number or structure of whole chromosomes, such as the trisomy 21 of Down syndrome.

The richness of species and their genetic differences on Earth, the basis of stable ecosystems.

The science of sorting organisms into hierarchical groups by their similarities and phylogenetic relationships.

Naming each species with two Latin words, genus plus species, printed in italics, as in Homo sapiens.

An identification tool offering a pair of mutually exclusive features at each step, leading step by step to a species name.

A naturally interbreeding population producing fertile offspring — the basic unit of classification.

The process by which populations split into new species through heritable variation and isolation.

The evolutionary mechanism by which better-adapted individuals leave more offspring and favourable traits build up over generations.

The differences among individuals of a species; heritable variation is the precondition of natural selection.

Organs in different organisms sharing the same origin and basic structure but different functions — evidence of common ancestry.

Ancient remains and traces preserved in rock strata, showing the changing sequence of life through time.

A tiny outgrowth of a root epidermal cell, greatly enlarging the surface for absorbing water and minerals.

The net movement of water molecules across a partially permeable membrane from a dilute to a concentrated solution.

Moving substances across membranes against the concentration gradient, spending energy from respiration.

The pair of cells framing each stoma, opening or closing it as they swell with water or go limp.

The loss of water as vapour, mainly through the stomata of leaves.

The negative pressure created as water evaporates from mesophyll cells — the main force hauling water up the xylem.

Hollow tubes of dead cells with lignified walls, carrying water and minerals upward only and doubling as support.

Living conducting tissue that transports organic food both up and down the plant.

The apparatus measuring a shoot's water uptake, and hence estimating the rate of transpiration.

The firm state of cells pressing cytoplasm against the wall when full of water — a key support for herbaceous plants.

Asexual reproduction through vegetative parts such as roots, stems and leaves, giving offspring genetically identical to the parent.

The male reproductive part of a flower, a filament topped by the pollen-producing anther.

The female reproductive part of a flower — stigma, style and an ovary holding the ovules.

The pollen-producing, pollen-holding tip of the stamen.

The transfer of pollen from anther to stigma of the same or another flower, by insects or wind.

The tube a pollen grain grows down the style to the ovule, carrying the sperm through it.

The fusion of sperm with the egg cell inside the ovule, forming the zygote that starts the seed.

The spreading of seeds or fruits away from the parent, by wind, water, animals or self-ejection.

The resumption of growth in a seed given suitable water, oxygen and warmth, developing into a seedling.

The plant hormone made in shoot tips; at low concentration it promotes cell elongation and controls phototropism and apical dominance.