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4.6& 4.7 biodiversity within a community & investigating diversity…
4.6& 4.7 biodiversity within a community & investigating diversity
4.6 lesson 1: index diversity
definitions
species
a group of similar organisms that are able to reproduce to give fertile offspring
population
the number of individuals of a particular species in a particular area at a particular time
ecosystem
the biotic (living) and abiotic (non-living) things in an area and the interactions between them
community
all the populations of all the different species of an organism
habitat
where the organism usually lives
species richness
the number of different species in a community (common measure of biodiversity)
index of diversity
the relationship between the number of species in a community and the number of individuals in each species (better measure of biodiversity)
calculate index of diversity
N = total number of organisms of all species
n = total number of organisms of each species
how to explain index of diversity
the number of individuals of each species in community x is more evenly spread than in community y therefore index diversity is higher/ community id more bio-diverse
4.6 lesson 2: impact of agriculture on biodiversity
key issues
removal of hedgerows, ponds, woodlands, tress, marshes , weeds etc to provide more land for farming reduces habitats and biodiversity - creates monoculture
pollution from use of artificial pesticides herbicides and fertilisers kills plants and animals therefore reducing biodiversity
ploughing destroys roots and fungal networks in the soil
intensive grazing of uplands has reduced woodland and biodiversity
cutting and fertilising grasslands decreases plant insect and other animal biodiversity
solutions
using natural fertilisers/compost and rotating cereal crops with legumes can restore nitrate levels in the soil without use of fertilisers
rotating crops reduces disease and pests and therefore need for pesticides
not ploughing improves soil structure holds water which improves drought tolerance
mob grazing allows time for plants to recover
cutting grasslands later allows flowering and improves plant species biodiversity
restoring habitats within farms e.g field margins/hedgerows etc improves biodiversity and biological control of pests
natural versus agricultural ecosystems
natural
complex communities
large number of different species
high index diversity
agricultural
controlled by humans
genetic variety of alleles and number of species is reduced to the few that display the desired characteristics
large biomass taken up by desirable species so reduces area available to other species
low index of diversity
4.7 lesson 1: genetic diversity
genetic diversity definition
all the different alleles in a population
measuring genetic diversity within a population
to measure genetic diversity we can look at the variety of measurable and observable characteristics within a population e.g size
however many characteristics are polygenic (controlled by more than one gene) and characteristics are often affected by the environment
because of new technology we now measure genetic diversity by looking at variation in:
base sequence of DNA
base sequence of mRNA
amino acid sequence of proteins
this produces continues variation and makes it difficult to determine how many alleles are affecting the characteristic
rationale behind using observable characteristics as a measure for genetic diversity
based on the fact that each observable characteristic is determined by a gene or genes
the variety within a characteristic depends on the number and variety alleles of that gene
phylogenetic classification
evolutionary relationships (how closely relayed two species are) are determined by comparing:
physical characteristics
DNA base sequences
mRNA base sequences
amino acid sequences
shapes of self antigens/antibodies
limitations of using observable characteristics
large number of observable characteristics are coded for by more than one gene (they are polygenic) which means they are not discrete from one another and vary continuously
characteristics can also be modified by the environment so differences may be due to different environmental conditions rather than alleles
DNA sequencing
accurately determines the exact order of nucleotide bases on DNA
each nucleotide is marked with a different coloured fluorescent dye
what causes differences in DNA sequences
differences in DNA sequences build up over time due to mutations, the sequences of nucleotide bases in the DNA of the new species will change. consequently over time new species will accumulate more and more differences in its DNA
