Estonian Basic-School Biology Exam flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Species

A group of organisms that can interbreed and produce fertile offspring under natural conditions; the species name is written as Genus plus species, for example Homo sapiens.

Prokaryote

A cell without a membrane-bound nucleus or membrane-bound organelles, having circular DNA in a nucleoid and 70S ribosomes; bacteria and archaea are prokaryotes.

Fungal cell wall

The rigid outer layer of fungal cells made of chitin, which distinguishes fungi from plants whose walls are cellulose and from bacteria whose walls contain peptidoglycan.

Vertebrate classes

Fish, amphibians, reptiles, birds and mammals; all have a backbone and internal skeleton, and they differ in skin covering, thermoregulation, fertilisation mode and respiratory organs.

Mitochondrion

An organelle with a double membrane where aerobic respiration produces ATP from glucose and oxygen; abundant in muscle and liver cells that need large amounts of energy.

Selective permeability

The property of a cell membrane that allows some substances to pass while restricting others, controlled by the phospholipid bilayer and embedded transport proteins.

Osmosis

The diffusion of water across a selectively permeable membrane from a region of higher water potential to one of lower water potential, requiring no energy input.

Tissue

A group of similar cells with a common structure and function, such as epithelial, connective, muscle and nervous tissue in animals, or xylem and phloem in plants.

Stoma

A pore in the leaf epidermis surrounded by two guard cells; it opens to admit carbon dioxide for photosynthesis and closes to reduce water loss by transpiration.

Photosynthesis equation

6CO2 + 6H2O + light energy yields C6H12O6 + 6O2; it occurs in chloroplasts containing chlorophyll, converting light energy into chemical energy in glucose.

Xylem and phloem

Xylem transports water and dissolved minerals upward from roots to shoots; phloem transports sugars and other organic compounds from leaves to other plant parts.

Pollination

The transfer of pollen from an anther to a stigma, by wind, insects, birds or water; it precedes fertilisation, which produces seeds and fruit in angiosperms.

Countercurrent gill flow

Water flows over fish gills in the opposite direction to blood, maintaining a concentration gradient along the whole gill and maximising oxygen uptake from water.

Closed circulatory system

A system in which blood stays within vessels and the heart pumps it around the body; found in annelids, cephalopods and all vertebrates, unlike the open systems of insects.

Metamorphosis

A change in body form during development; complete metamorphosis has egg, larva, pupa and adult stages as in butterflies, incomplete metamorphosis lacks the pupal stage.

Alveolus

A tiny air sac in the lungs with a thin, moist wall and dense capillary network, where oxygen diffuses into the blood and carbon dioxide diffuses out.

Nephron

The functional unit of the kidney; it filters blood in the glomerulus, reabsorbs water and glucose, and secretes wastes to form urine.

Negative feedback

A control mechanism in which a change from the normal value triggers a response that reverses the change, keeping conditions such as body temperature and blood glucose stable.

Reflex arc

The pathway of a reflex: receptor, sensory neuron, interneuron in the spinal cord, motor neuron and effector; it produces a rapid automatic response without conscious decision.

Allele

One of two or more alternative forms of a gene occupying the same locus on homologous chromosomes; alleles may be dominant or recessive and determine the phenotype in combination.

Genotype and phenotype

Genotype is the combination of alleles an organism carries, such as Aa; phenotype is the observable characteristic produced by that genotype interacting with the environment.

Monohybrid cross

A cross following one pair of contrasting traits; crossing two heterozygotes Aa × Aa gives offspring in a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio.

Sex-linked inheritance

Inheritance of genes located on sex chromosomes, usually the X; recessive X-linked traits such as colour blindness appear more often in males because they have only one X.

Meiosis

A reduction division producing four haploid gametes from one diploid cell; crossing over and independent assortment of chromosomes create genetic variation in the offspring.

Natural selection

The process by which individuals with heritable traits that improve survival and reproduction leave more offspring, so those alleles become more common in later generations.

Homologous structures

Body parts with the same basic structure and origin but different functions, such as the forelimbs of humans, whales and bats; they indicate common ancestry.

Speciation

The formation of new species when populations become reproductively isolated, for example by a geographic barrier or by polyploidy, so gene flow between them stops.

Trophic level

The position an organism occupies in a food chain, such as producer or primary consumer; only about ten per cent of energy passes from one level to the next.

Carrying capacity

The maximum population size of a species that an ecosystem can sustain indefinitely with the available food, water, space and other resources.

Eutrophication

Nutrient enrichment of water, usually by fertiliser runoff, causing algal blooms; decomposition of the algae depletes oxygen and can kill fish and other organisms.

Controlled variable

A factor kept constant across all experimental groups so that the effect measured can be attributed to the independent variable rather than to other influences.

Reliability

The consistency of results when a measurement or experiment is repeated; it is increased by taking multiple readings and calculating a mean, and is distinct from validity.