Biodiversity✅ Flashcards
define biodiversity
the variety in life in an area, which can be measured in terms of genetic species or habitat diversity
what is measured in genetic diversity
an estimate of gene variants (alleles) in a species
what is measured in species diversity
two components are measured:
species richness (number of species in an area)
species evenness ( number of individuals of each species)
what is measured in habitat/ecosystem diversity
number of different habitats (or ecosystems) in an area. Hardest measure to calculate in biodiversity because boundaries of ecosystems are often difficult to determine with accuracy
describe the difference between a population and a community (2 marks)
population: a group of organisms of the same species
Community: a set of populations within an ecosystem
suggest and explain which measure of biodiversity is most significant when assessing the health of one ecosystem (3 marks)
species biodiversity
because the variety and abundance of species within the ecosystem indicates the stability and health of food chains
explain how a habitat can contain many specie but its biodiversity is considered low (3 marks)
species richness might be high
but a few species might dominate/many species have low numbers
biodiversity based on both species richness and species evenness
what principles should you bear in mind when designating a sample method
larger sample size- more representative of whole ecosystem
avoiding bias-when choosing where to take samples will increase validity of results
sampling can only be claimed to be a representative estimate of an ecosystem biodiversity
what is random sampling, how do you decide the location of sampling points
random sampling avoids bias, can produce unrepresentative picture of ecosystem
generating random numbers, which are used as grid coordinates
taking samples from these coordinates
what is stratified sampling
study site divided into smaller areas, based on distribution of habitats, this sampling is more representative of the ecosystem and reduces sampling error
what is systematic sampling
a transect is used where environmental gradients exist (eg soil pH). You can investigate whether the distribution of organisms also changes across the habitat
state 3 factors that might limit the sample size in ecological survey (3 marks)
time
money
labour availability
access (to the ecosystem)
equipment
outline how you would estimate the abundance of plant species from a rocky shoreline to the edge of sand dunes 30M inland (4 marks)
Belt transect
line placed along the ecosystem (from shoreline to edge of sand dunes)
quadrats used at intervals
abundance of each species estimated (eg by percentage cover)
what animals and how is pooter and sweep nets technique used for sampling
Pooter: used on insects, insects sucked into a chamber
Sweep nets: used on insects in long grass, net is swept through the habitat
what animals and how is pitfall traps, tree beating and kick sampling techniques used for sampling
pitfall traps: used on small, crawling invertebrates, a hole in the ground traps organisms
tree beating: used on tree-dwelling invertebrates, trees are shaken and organisms fall on a sheet
Kick sampling: used on river-dwelling organisms, a river bed is disrupted and organisms are captured in a net
how are plants sampled, what 2 ways can they be recorded
using quadrats
1. count absolute number of individuals in the quadrat
2. estimate % of a quadrat covered by a species
how can wind speed, light intensity and temperature be measured
wind speed=anemometer, ms^-1
light intensity=photometer, lux
temperature=thermometer, degrees
pitfall traps are covered. suggest why (1 mark)
to prevent rainwater from entering and drowning trapped organisms
suggest why the % coverage of a species rather then its density might be recorded (2 marks)
time limitations
in cases where individuals of a species are difficult to count
what is used to calculate species diversity
Simpsons diversity index (D)
D=1-[sum of (n/N)^2]
n=number of individuals of a particular species
N= total number of all individuals of all species
suggest why an ecosystem with a low value of D is vulnerable to environmental change (3 marks)
few species/ low numbers in many of all species
an environmental change may cause the loss of species from the ecosystem
why can genetic diversity of a population increase
DNA mutation
gene flow from another population (ie breeding between populations of same species)
how can genetic diversity decrease in a population
selective breeding
captive breeding
genetic bottlenecks (ie when a population is reduced to a small size because of disease, habitat destruction, or migration)
how can genetic diversity be measured/ what methods
number of alleles per gene
heterozygosity: the proportion of individuals in a population that have 2 different alleles for a particular gene
the proportion of genes for which more than 1 allele exists. a gene that has 2 or more possible variants/alleles is known as a polymorphic gene, a gene for only 1 variant/allele called a monomorphic gene