WJEC Biology: Unit 2- Definitions

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Absorption
The passage of molecules and ions through the gut wall into the capillaries or lacteals
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Affinity
The degree to which a molecule has a chemical attraction to another
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Analogous Structures
Structures that share the same function but have a different origin
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Apoplast Pathway
The pathway of water through the cell walls in a plant
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Atrio-Ventricular Node
The area of tissue in the wall of the heart between the atria and ventricles, through which a wave of electrical excitation is passed through the atria to conducting tissue in the walls of the ventricles
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Autotroph
An organism that makes its own complex organic molecules via photosynthesis or chemosynthesis (Plants)
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Binomial System
A naming system that gives an organism two names, the name of its genus followed by species
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Biodiveristy
A measure of the number of different species and the number of individual species in a specific region
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Bohr Effect
The reduction in affinity of haemoglobin for oxygen at higher partial pressures of CO2, moving the dissociation curve to the right
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Carnassials
The last upper pre-molar and first lower molar teeth of a carnivore
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Chloride Shift
The diffusion of chloride ions from the blood plasma into the red blood cell, preserving electrical neutrality
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Cohesion-Tension Theory
The theory of the mechanism by which water moves up the xylem, as a result of the cohesion and adhesion of water molecules and the tension in the water column
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Convergent Evolution
The development of similar features in unrelated organisms over long periods of time, related to natural selection of similar features in a common environment
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Cooperative Binding
The increasing affinity of a haemoglobin molecule for oxygen as the 2nd and 3rd oxygen molecules bind to it
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Counter-Current Flow
The process in bony fish where blood and water flow in opposite directions at the gill lamellae
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Diastole
A stage in the cardiac cycle where the heart muscle relaxes
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Digestion
The breakdown of large insoluble food molecules into smaller soluble molecules that are small enough to be absorbed
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Divergent Evolution
The development of different structures over long periods of time, from the equivalent structures in related organisms
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Domain
The highest taxon in biological classification (Eubacteria, Archaea and Eukaryota)
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Double Circulation
A circuit in which blood passes through the heart twice
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Egestion
The elimination of undigested waste (Shit)
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Endodermis
A single layer of cells around the pericycle and vascular tissue of the root that houses the casparian strip
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Genus
A taxon containing organisms with many similarities, but enough differences that they are not able to interbreed to produce fertile offspring
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Heterotroph
An organism that consumes ready-made complex organic matter (food) i.e Animals
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Holozoic
The feeding method of many animals, involving: ingestion, digestion and egestion
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Ingestion
Taking in food at the mouth
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Kingdom
The second highest taxon where all living organisms are classified into five kingdoms based on their physical features
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Lymph
Fluid absorbed from between the cells into lymph capillaries
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Mutualism
A relationship between two different organisms to their mutual advantage
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Myogenic
The intrinsic contraction of cardiac muscle initiated from within the heart
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Natural Selection
The process whereby organisms better adapted to their environment survive and produce more offspring
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Operculum
The covering over the gills of a bony fish
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Parallel Flow
The process in cartilaginous fish where blood and water flow in the same direction at the gill lamellae
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Parasite
An organism that obtains nutrients from another living organism, to which it causes harm
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Peristalsis
The contraction of circular and longitudinal muscle in the gut wall that moves food in one direction
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Phloem
Plant tissue containing sieve tube elements and companion cells, translocating the products of photosynthesis from source to sink (Sucrose and Amino acids)
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Phylogenetic Tree
A diagram that shows the descent of different organisms with the branch points representing common ancestors
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Phylum
The third highest taxon which is a subdivision of a kingdom
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Polymorphism
The occurrence of more than one phenotype in a population
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Potometer
A device which directly measures the rate of water loss during transpiration by measuring the rate of water uptake
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Root Pressure
The upward force on water in roots, derived from the osmotic movement of water into the root xylem
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Rumen
The largest chamber in the gut of ruminant herbivores, in which mutualistic microbes digest complex polysaccharides
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Ruminant
A cud-chewing herbivore possessing a stomach that divides into four chambers
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Saprotroph
Organisms that feed on dead or decaying matter by extracellular digestion and absorption of the products of digestion
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Sieve Tube Element
A component of the phloem where the products of photosynthesis can be translocated up, down or sideways through the plant
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Single Circulation
A circuit where blood passes through the heart once in its circuit around the body, e.g. in fish
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Sino-Atrial Node
An area of the heart muscle in the right atrium that initiates a wave of electrical excitation across the atria, to generate contraction of the heart muscle (The pacemaker)
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Species
A group of organisms that are able to interbreed and produce fertile offspring
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Symplast Pathway
The pathway of water through the cytoplasm in a plant
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Systole
A stage in the cardiac cycle in which heart muscle contracts
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Tissue Fluid
The plasma without the plasma proteins, forced through the capillary walls and filling the spaces between them
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Tracheid
Spindle-shaped, water-conducting cells in the xylem of ferns, conifers and angiosperms
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Transpiration
The evaporation of water from the above-ground parts of the plant, out through the stomata and into the atmosphere
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Ventilation
A mechanism enabling air or water to be transferred between the environment and a respiratory surface
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Vessel
Water-conducting structures in angiosperms made of cells fused end-to-end making hollow tubes, with thick cell walls made of lignin
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Other cards in this set

Card 2

Front

The degree to which a molecule has a chemical attraction to another

Back

Affinity

Card 3

Front

Structures that share the same function but have a different origin

Back

Preview of the back of card 3

Card 4

Front

The pathway of water through the cell walls in a plant

Back

Preview of the back of card 4

Card 5

Front

The area of tissue in the wall of the heart between the atria and ventricles, through which a wave of electrical excitation is passed through the atria to conducting tissue in the walls of the ventricles

Back

Preview of the back of card 5
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