4.11 - Biodiversity Flashcards
(30 cards)
Biodiversity
the variety of living organisms present in an area
habitat biodiversity
The number of different habitats found within an area
- each habitat can support a number of different species so in general, the greater the habitat biodiversity, the greater the species biodiversity
Components of species biodiversity
species richness = the number of different species living in an area
species evenness = a comparison of the numbers of individuals in each species living in a community
Genetic biodiversity
- the variety of genes that make up a species
- different alleles existing results in genetic biodiversity within a species, leading to different characteristics being exhibited, leading to better adaptation to a changing environment
Sampling
- taking measurements of a limited number of individual organisms present in a particular area
- can be used to estimate the number of organisms in an area (abundance) or a particular characteristic of an organism
Random sampling
- selecting individuals by chance, each individual in the population has an equal likelihood of selection
- random number tables or computers used
Non-random sampling
- the sample is not chosen at random
- opportunistic (weakest as may not be representative), uses organisms that are conveniently available
- stratified, random sample taken from strata proportional to its size
- systematic, sampling different areas within an overall habitat, often using a line or belt transect
Line transect vs belt transect
- line transect = marking a line along the ground between two poles and taking samples at specific points
- belt transect = two parallel lines are marked and samples are taken in the area between the two lines, provides more information
sampling bias and chance
- selection process may be biased, bias can be reduced using random sampling so human involvement in choosing the samples is removed
- organisms selected may by chance be not representative of the population. Chance can never being completely removed, but its effect can be minimised by using a large sample
Techniques for sampling animals
- pooter, insects drawn into the holding chamber by sucking on a mouthpiece
- sweep nets, used to catch insects in areas of long grass
- pitfall traps, hole dug in ground covered by roof structure to catch crawling invertebrates
- tree beating, shaken t0o dislodge invertebrates ;living in a tree or bush
- kick sampling, river bank is kicked and there is a net downstream
Sampling plants
Using a quadrat:
- point quadrat, a frame containing a horizontal bar. Long pins are pushed through the bar at set intervals and plants that touch the pin are recorded
- frame quadrat, a square frame divided into a grid of equal sections. The type and number of species within each section is recorded. Can measure density, frequency and percentage cover
Simpson’s index of biodiversity
- allows us to calculate biodiversity, taking both species richness and species evenness into account
- 0 = no biodiversity, only 1 species present in a habitat
- 1 = highest biodiversity, exactly the same population of each species
Estimating animal population size
- capture-mark-release-recapture
- involves capturing as many individuals of a species in an area as possible and then marking and releasing them
- time is allowed for the organisms to redistribute themselves
- another sample of animals are collected
- by comparing the number of marked and unmarked individuals in the sample, scientists can estimate population size
measuring abiotic factors
- wind speed = anemometer
- light intensity = light meter
- relative humidity = humidity sensor
- pH = pH probe
- temperature = temperature probe
- oxygen dissolved in water = dissolved oxygen probe
Why are electronic sensors advantageous for measuring abiotic factors
- rapid changes can be detected
- human error in taking a reading is reduced
- a high degree of precision can often be achieved
- data can be stored and tracked on a computer
Typical habitat features for environments with low biodiversity
- relatively few successful species
- stressful and/or extreme environment with relatively few ecological niches
- the few species that live in the habitat often have very specific adaptations for the habitat
- relatively simple food web
- a change to the environment would have major effects on the ecosystem as a whole
Typical habitat features for environments with high biodiversity
- a large number of successful species
- not a stressful environment with more ecological niches
- many species live in the habitat, with few specific adaptations to the environment
- complex food web
- a change to the environment would have a relatively small effect on the ecosystem as a whole
Factors that affect genetic biodiversity
Increase:
- mutations creating new alleles
- interbreeding between different populations, alleles are transferred between the two populations (gene flow)
Decrease:
- selective breeding/artificial selection
- captive breeding programs in zoos
- rare breeds
- artificial cloning (asexual reproduction)
- natural selection
- genetic bottlenecks (very few members of the population survive an event or change)
- the founder effect - a small number of individuals created a new colony geographically isolated from the rest
- genetic drift (some alleles are lost due to the random nature of inheritance)
Measuring genetic biodiversity
Measure the proportion of genes that are polymorphic (more than 1 allele)
proportion of polymorphic gene loci = number of polymorphic gene loci / total number of loci
Human influence on biodiversity
- deforestation, directly reduces the number of trees present, reduces habitat diversity if one tree type is felled, animals forced to migrate
- agriculture, monoculture, deforestation, removal of hedgerows, pesticides and herbicides
- climate change, extinction of species living in arctic regions, saltwater encroaching on freshwater habitats from sea level rise, loss of non-drought resistant plants, loss of insects or spread of tropical diseases from insect migration
Aesthetic reasons for maintaining biodiversity
- inspiration for artists
- natural environment reduces stress
Economic reasons for maintaining biodiversity
- soil erosion and desertification as a result of deforestation may reduce abilities to grow crops, leading to resource and economic dependence on other countries
- conservation of ‘useful’ organisms used to make things
- species with economic potential may become extinct before discovered (chemically or medically useful)
- continuous monoculture results in soil depletion, weakening crops, farmers become more reliable on expensive pesticides and fertilisers
- high biodiversity provides protection against abiotic stresses
- high biodiverse areas attract tourism
- wild varieties of plants are needed for genetic engineering to make crops more viable
ecological reasons for maintaining biodiversity
- removal of one species may have a significant effect on others, as species within ecosystems are interdependent on each other
Keystone species
An organism that has a major influence on the way its ecosystem works.
There are three types:
- predators
help control the populations of prey species, which in turn affects the quantity of plants and animals further along the food web
- ecosystem engineers
an organism that creates, changes, or destroys a habitat e.g. beavers
- mutualists
two or more species in an ecosystem interact for each other’s benefit, such as bees and flowering plants
