Whole of Unit/Module 4 Genetic information, variation and relationships between organisms for AQA A level Biology based on class notes, specification, textbooks, websites, videos and revision sessions. Summarised into bullet point notes that are quick and to the point with just information you need...
variety in an ecosystem
variety of habitats and variety of species
What is Species Diversity?
number of different species
number of individuals for each species
What is Genetic Diversity?
variety of alleles in a species population
the larger number of individuals in a species, the larger the genetic diversity
Benefit of high species diversity?
Stable ecosystem
each species is less likely to become extinct (due to high genetic diversity)
& if a species does become extinct it will not affect the food chain as there are other
species available
How to measure Species Diversity for an area?
Species Diversity Index
takes into account the number of different species and how many individuals there are
for each species
the larger the species diversity index, the larger the species diversity
How does deforestation lower species diversity?
(deforestation is the removal of trees for wood & space)
decreases plant species diversity
less variety of habitats/niches
less variety of food sources
decreases animal species diversity
How does agriculture/farming lower species diversity?
deforestation to make space for farm
only grow a few plants & keep a few animal species
selectively breed plants & animals
use pesticides to kill other species
What is Classification? placing organisms into groups
, What is Hierarchical Classification?
large groups divided into smaller groups with no overlap
domain, kingdom, phylum, class, order, family, genus, species (dear kevin please come
over for good supper)
What is Binomial Naming System?
using Genus name and Species name to name organism
Genus name first in capital, Species name second in lower case
e.g. tiger = Felix tigris
What is a Species?
a group of individuals with similar characteristics that can interbreed to produce fertile
offspring
Why are the offspring from 2 different species mating infertile?
offspring will have a odd number of chromosomes
therefore, cannot perform meiosis, cannot produce gametes
example: horse + donkey = mule,
mule is infertile,
horse has 64 chromosomes/donkey has 62 chromosomes,
horse gamete has 32 chromosomes/donkey gamete has 31 chromosomes,
therefore, mule has 63 chromosomes
What is Phylogenetic Classification?
based on evolutionary relationships – how closely related different species are and how
recent a common ancestor they have
3 ways of comparing relationship between different species?
DNA Hybridisation: comparing DNA base sequence
- take DNA from 2 species to be compared
- radioactively label one of the DNA
- heat both sets so double strand separates
- cool so single strands join together
- look for Hybrid DNA (one strand from species A, one strand from species B)
- identify Hybrid DNA by 50% radioactivity
- heat Hybrid DNA to measure similarity
results = higher temperature required
more hydrogen bonds present
more complementary base pairing
more similar the base sequence
more similar the species
more closely related
more recent a common ancestor
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