ABIOTIC & BIOTIC FACTORS

ABIOTIC FACTORS

Factor		Description
climate
	temperature	biochemical processes occur over a narrow range of temperatures need adaptations to combat or avoid extremes
	water	organisms dependant on  abundant water supply need to live in environments that supply the water, or have adaptations that conserve water
	light	essential for all green plants and photosynthetic bacteria plants have adaptations for obtaining optimum illumination
	humidity	effects the rate at which water evaporates from the surface of organisms effects the ability to retain water and resist drying out
	wind and air currents	particularly applies to plants - need strong stems and root systems to live in exposed places also effects evaporation rate instrumental in dispersal of spores and seeds
soil
	pH	influences distribution of plants in soil and freshwater most are highly sensitive to changes in pH
	mineral salts and trace elements	particularly affect distribution of plants in the soil some organisms require methods for gaining those that are lacking , e.g. harboring nitrogen-fixing bacteria, catching and digesting insects many elements are toxic when in (very) high concentrations this can limit distribution
	water retention/absorption	the proportion of clay, sand and vegetative matter in soils affects the ability of soils to retain and/or absorb water this can limit the species of plants that can grow in the soil it can also limit the animals that are able to live in the soils, or burrow and/or make their "homes" in the soils
geography
	water currents	particularly in streams and rivers many adaptation to cope with strong currents enable organisms to anchor themselves or to avoid currents
	salinity	sharp distinction between marine and freshwater species, and the distribution of estuarine animals special physiological or behavioural adaptations for withstanding daily fluctuations in salinity that accompany tidal flow utilised by some species that are adapted to cope with changes in salinity to rid themselves of parasites by entering estuarine areas
	wave action	particularly affects organisms living in the inter-tidal zone adaptations needed to withstand buffeting by waves and exposure at low tide e.g. sessile habit of animals (limpets and sea anemones), burrowing (shrimps, worms, pippies and sand hoppers), ability to cement themselves to rocks (seaweeds, barnacles and oysters)
	topography	minor differences in position can be as important as major geographical separation e.g. centre and edge of a stream, upper and lower sides of rocks, north and south-facing rock ledges
	background	shape and/or colour allow some organisms to be camouflaged when viewed against some backgrounds (including other organisms) general texture and pattern of the environment particularly insects, amphibians and reptiles
	shelter	availability of places that reduce exposure to adverse environmental conditions or predators
other chemical factors
	oxygen
	carbon dioxide
	nitrogen
	phosphorus
	sulfur

BIOTIC FACTORS

• 10 types of biological relationships

Relationship/Factor	Description
mutualism	both organisms benefit
co-operation	both benefit but they are not dependent on each other
commensalism	one organism benefits, but the other is not harmed
amensalism	one organism inhibits the other
parasitism	one organism is dependent for nutrition on the other, to the detriment of the host
predation	one organism attacks and kills the other for food
competition	rivalry by organisms of the same (intraspecific) or different (interspecific) species for a resource/s, e.g. food, shelter, mate, light, air, water, space
camouflage	the ability of an organism to remain undetected by other organisms due to coloration or shape, used to assist in hunting prey or to protect against predation
mimicry	resemblance of one organism to another (colour, shape or behaviour), usually a defense against predation
humans	Man's influences on an ecosystem may be the most dramatic and often the most threatening to the survival of other organisms due to his ability to alter the physical environment and to compete  with and prey on other organisms. Man also possesses the ability to alter/engineer the characteristics of other organisms to suit his purposes by breeding desired characteristics and more recently by directly altering their  genetic code.

Questions:

1. Compare the difference in features of mesophytic, sclerophytic and xerophytic plants and relate them to the abiotic and biotic features of their environments.
2. Collect specimens (or use pictures if samples are not available) of plants from each of the groups (mesophytes, sclerophytes & xerophytes) and draw and label their features noting the differences and similarities.
3. Describe the natural vegetation of your area and relate it to the abiotic features of the environment.