Chapter 11 - Biodiversity Flashcards
Define abiotic
Non living
Define biodiversity
Variety of living organisms present in an area
Define species
Smallest + most specific taxomic group
How can biodiversity be assessed
o The number and range of different ecosystems and habitats
o The number of species and their relative abundance
o The genetic variation within each species
What is habitat diversity
• range of different ecosystems or habitats within a particular area or region
What is species richness
number of species within an ecosystem
What is species diversity
number of different species in an ecosystems + the evenness of abundance across the different species present
What is species evenness
evenness of abundance across the different species present
What will increase the species diversity
greater the number of species in an ecosystem + more evenly distributed the number of individuals from each species
How can an ecosystem have a lot of different species but not have a high species diversity
some species may be very rare in ecosystem = does not necessarily have high species diversity
A more stable ecosystem…
high species diversity
Why does a low species diversity make an unstable ecosystem
If pathogen targets one of the species = whole population could be wiped out + ecosystem collapses
What is genetic diversity
diversity of alleles and genes in the genome of species
How to measure genetic diversity
by working out the proportion of genes that have more than one form (allele) + how many possible alleles each gene has
Why may there be genetic differences between populations of the same species
because the two populations occupy slightly different ranges in their habitat = subject to different selection pressures = affect the allele frequencies in their populations
Why is genetic diversity within a single population important
help the population adapt to, and survive, changes in the environment
Negatives of inbreeding
leads to a high proportion of individuals being homozygous (e.g. AA to aa) for many genes, resulting in lower genetic diversity
o This can mean that genetic diseases caused by recessive alleles can become more common in these populations
What is sampling
a method of investigating the abundance and distribution of species and populations
Two types of sampling
o Random
o Non-random
What is random sampling used for
to estimate the distribution and abundance of species
What is the distribution of a species
how it is spread throughout the ecosystem
What is the abundance of a species
number of individuals of that species
How to carry our random sampling - Quadrats
- Use Quadrats
- convert sampling area into grid
- use random number generator = quadrats
- record abundance / percentage cover
What are Quadrats used for
suitable for sampling plants or slow-moving animals
Other methods for sampling
- sweep nets
- pitfall traps
- pooters
- tullgreen funnel
- kick sampling
Sweep nets
large, strong nets with a fine material (very small holes) that are used to catch flying insects and insects that live in long grass by sweeping the net back and forth through the grass
Pitfall trials
cans or jars that are buried in the ground that are used to catch ground-dwelling (often nocturnal) insects and other invertebrates as they fall into the trap
Modification in pitfall
- canopy = stop trap filling with water
- newspaper / leaves = allow smaller insects to hide from predatory ones
Pooters
small plastic or glass containers with two tubes sticking out that are used to suck up small insects and other small invertebrates
first tube is placed over the insect and the second tube is used by the scientist to create suction
Tullgren funnel
funnels with a light bulb above and a container below that are used to collect invertebrates that live in leaf litter or soil.
leaf litter / soil is placed in the funnel and the light and heat forces the invertebrates to move down until they drop into the container
Kick sampling
used to catch freshwater invertebrates living in streams or rivers.
net placed on the stream-bed so that the water is flowing into it and the stream-bed just above the net is kicked
invertebrates are carried by the stream into the net
Types of non random sampling
• Opportunistic
• Stratified
• Systematic
Opportunistic
• choosing sampling locations based on various non-random factors = most convenient
Stratified sampling
• population is divided into subgroups or strata based on certain characteristic.. The subgroups are then sampled in proportion to their size or importance in the population = random within each strata
Systematic sampling
• method of sampling where every nth member of a population is selected for inclusion in the sample. The sampling interval or “n” is determined by dividing the population size by the desired sample size = random or non random? = no patterns in the data
How to do Quadrats non randomly
Using transects
How to use line transects
o Lay out a measuring tape in a straight line across the sample area
o At equal distances along the tape, record the identity of the organisms that touch the line. For example, every 2m
How to use belt transects
o Place quadrats at regular intervals along the tape and record the abundance or percentage cover of each species within each quadrat
What is species richness
measure of the number of different species within a given area
Problem with species richness
can be a misleading indicator of diversity as it does not take into account the number of individuals of each species
What is spedier evenness
• measure of the relative abundance of the different species within a given area
Why is this an example of the problems with species richness
• In the example above , Area 1 and Area 2 both contain 4 tree species
• However, Area 2 is actually dominated by one species and in fact, one of the species is very rare (only one individual)
• Although the two areas have exactly the same species richness, Area 1 has a higher species evenness (and therefore a higher overall species diversity) than Area 2
How to measure species richness
count the number of different species present.
How to measure species evenness
count the number of different species present and the number of individuals of each species
What is Simpsons index formula
You get in exam
What do all the variables mean in Simpsons index
• n = total no. of organisms for a single species
• N = total no. of organisms for all species
How to use this formula - careful where the sum of is
o Step 1: First calculate n / N for each species
o Step 2: Square each of these values
o Step 3: Add them together and subtract the total from 1