Biodiversity

A measure of variation found in the living world

The range of habitats in which different species live e.g. woodland, meadows, streams

The range of organisms found in a habitat Species - a group of organisms that can freely interbreed to produce fertile offspring Species richness - the number of plant species Species evenness - the degree to which the species are represented

The variation between individuals belonging to the same species - Genetic variation can create breeds within a species

Can be done by selecting a small portion and studying - multiply up the numbers of individuals of each species found, in order to estimate the whole number sampling should cause as little disturbance as possible

Sample sites inside the habitat are randomly selected e.g. random number generators advantages - ensures that the data is not biased by selective sampling disadvantages - may not cover all areas of a habitat equally. Species with a low presence may be missed

Sampling decisions made before collecting data advantages - easier and quicker to collect data disadvantages - data may be biased, leading to an overestimate of biodiversity (if an area is picked because the researcher knows it contains a species)

Dividing a habitat into areas which appear different, and sampling each separately+ advantages - ensures that all different areas of a habitat are sampled and species are not under represented disadvantages - may lead to an over-representation of some areas - a disproportionate number of samples are taken

When samples are taken at fixed intervals across a habitat advantages - useful when the habitat has a gradient in an environmental factor disadvantages - only the species on the line or within the belt can be recorded, may miss species

a quadrat is a square frame used to define the size of a sample area For random sampling - generate random numbers and use the numbers as coordinates Percentage cover - Use of a point frame. Lower the frame into the quadrat and record any plants touching the needles. use at regular intervals along a quadrat to avoid bias

Stretching a long string or tape measure across the habitat and taking samples along the line Line transect - in a large habitat, recording plants touching the line at set intervals along it Interrupted belt transect - Using a quadrat at set intervals along the line to provide quantatative data at intervals Continuous belt transect - Placing a quadrat beside the line and moving it along to study the belt in detail

Sweep netting - sweeping net through vegetation in wide arcs - empty net onto a white sheet - suitable for vegetation that is not too woody - a pooter can be used to collect animals before they fly away

Spread a white sheet out under a branch, knock the branch with a stick - vibrations dislodge small animals

• a trap set in the soil to catch small animals • a small container buried in soil so animals moving on soil surface will fall in • water or paper to keep animals from crawling out

• Collects small animals from leaf litter • A light above the litter drives animals downwards as the litter warms up = fall through mesh into jar

• Used to collect flying insects at night • Ultraviolet light attracts insects = eventually fall into alcohol

can be trapped using a Longworth trap Total population can be estimated using (C1 * C2) / C3 C1 - marked animals first time C2 - marked animals second time C3 - already marked animals second time - estimate can be affected by animals that learn the trap is harmless and has food, or by animals that stay away - birds can be estimated using a ringing technique

As human population grows and demand for food and goods increases, we have a greater effect upon other species - we have learned to use the environment to our advantage - we alter ecosystems to provide food - we destroy and fragment habitats - using more resources - pollute the atmosphere

Natural vegetation is cleared, which reduces genetic biodiversity, species have less capacity to adapt to changing conditions - Modern agriculture relies upon monoculture and selective breeding to increase efficiency

a) a crop consisting of one strain of species - limited genetic diversity e.g. palm oil b) Selecting for specific breeds means that other breeds become rare and die out = genetic erosion

as climate changes, species are less able to adapt to changes in temperature and rainfall = results in slow migration of populations Selectively bred plants and animals are less likely to be able to adapt to changing conditions and are vulnerable to disease = efficiency of agriculture will decrease

When the last living member of a species ceases to exist - Human activites contribute to extinction e.g. hunting

• Organisms are interdependent, through food chains and relationships (predation, competition, parasitism, mutualism) • a change in one species’ population affects others = high biodiversity - greater stability, alternative food sources mean species can adapt to change low biodiversity - high risk

• They have a disproportionately large effect on their ecosystem e.g. predator removal, herbivore increase, overgrazing, population crash Plants can also act as keystone species e.g. improving soil moisture, providing habitat, supporting organisms example: beavers dams that they build have a huge effect on the habitat