specialization, e.g. odours, reduction of pollen, fusion of parts, enclosure of
nectar, e.g., hammer orchid, yucca
wind, e.g., reduction of floral parts, loss of nectar, separation of sexes,
e.g. festuca rubra
non-specialisation, e.g.- formation of groups of flowers with more or less
exposed nectar, e.g., bellis perennis
Reproductive barriers between species
Ecological isolation. Populations live in different habitats and do not meet.
Temporal isolation. Mating or flowering occur at different seasons or times of the day.
Behavioural isolation. Males and females of the different species are not attracted to each other.
Mechanical isolation. Structural differences in genitalia or flower prevent copulation or pollen transfer.
Gametic isolation. Female and male gametes fail to attract each other, or are inviable.
Hybrid inviability. Hybrid zygotes fail to develop, of fail to reach sexual maturity.
Hybrid sterility. Hybrids fail to produce functional gametes.
Hybrid breakdown. The offspring of hybrids have reduced viability or fertility.
The main parts of a flowering plant and their function.
Flower. Generation and reproduction. Can be hermaphrodite or bisexual, producing the pollen grain or containing the ovule, or both. Female and bisexual flowers produce the seed when they are fertilised.
Stem. Carries solutes from roots to leaves. Carries flood from leaves to other parts of the plant. Bears the leaves in a position for photosynthesis. Displays the flower for pollination. Exposes the seeds for dispersal.
Leaf. Respiration - taking in oxygen and giving out carbon dioxide and water. Transpiration - giving off excess water in the for of vapour. Photosynthesis - making food from light.
Roots. Anchor the plant to the substrate. Absorb inorganic salts in solution. Transports nutrients to leaves.
4 basic types of animal tissue
Epithelial - a sheet of cells that covers an internal or external surface, e.g. lining the lungs, skin
Connective tissue - binds and supports, e.g. bone, cartilage
Muscular tissue - specialises in contraction, e.g. smooth muscle tissue in the intestinal wall, cardiac muscle tissue
Nervous tissue - specialised to receive stimuli and conduct inputs from one region to another, e.g. neurons