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Title: Diversity, Classification and Variation Summary
Description: Summary of topic 4B from A Level Biology AQA Revision book
Description: Summary of topic 4B from A Level Biology AQA Revision book
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Diversity, Classification and
Variation
Created
@February 15, 2025 4:20 PM
Class
Cells to Systems
DNA Passing Down Generations
Gametes form sperm cells and egg cells
Forms zygote during fertilisation and develops into organism
Body cells have two of each chromosome, one from each parent
Haploid number of chromosomes means one copy of each chromosome
Haploid sperm join with haploid egg at fertilisation
Sperm and egg fertilisation is randomised, producing zygotes with varied
chromosomes combinations
Results in species diversity
Gamete Formation from Meiosis
Two copies of each chromosome from DNA replication are called
chromatids
...
g ultraviolet radiation, ionising radiation, chemicals and viruses
High Amounts of Alleles Means High Genetic Diversity
Alleles are different versions of one gene
Genetic Diversity Increase
How many different alleles are present in a population/species
G
...
of various alleles in gene pool, genetic diversity decreases
Survivors reproduce to recreate peak population numbers
Natural Selection
Organisms have increased chances of survival if they have special allele
increasing survival rates
Majority of population inherits special, beneficial allele
Species more likely to survive and pass genes to offspring
Leads to evolution in future generations
Better Adaptations
Behavioural Adaptations
How organism acts increases survival rate and reproduction
Physiological Adaptations
Internal body processes increases organisms rate of survival
Anatomical Adaptations
Physical features on body increases survival chances
Diversity, Classification and Variation
5
Phylogeny
Study of evolutionary history in organisms
Tells us relatives of different species and how closely related they are
Evolved organisms share common ancestor
Classification
Eight levels used for classification
Groups sorted into hierarchy, largest group on top
Organisms belong to one group, avoids possible overlap
Species first sorted into ‘domain’ groups: Eukarya, Bacteria and Archaea
Relatives within domain are sorted into ‘kingdoms’, smaller groups
Groups continue down rest of the levels, but further down we are, they’ll
be fewer organisms present
Binomial Naming
Given single globally accepted name in latin, divided into two parts
First part= Genus name, contains capital letter
Second part= Species name starting with lower case letter
System used to avoid confusion
Courtship Behaviour
Used by organisms for attracting a partner
Only organisms of the same species will respond to mating specific mating
behaviour
Diversity, Classification and Variation
6
Method allows recognition between organisms of same species and
prevents interbreeding
This behaviour can be used as classifying method
Similarities in courting behaviour means organisms are more closely
related
Clarifying Evolutionary Relationships Techniques
Genome Sequencing
Advancements in technique means whole DNA base sequences can
be recognised
Comparisons can be made of sequences determining the extent of
close relations between organisms
Comparing Amino Acid Sequences
Related organisms have similar acid sequences
More similarities between amino acid sequences, more closely related
the organisms are
Immunological Comparisons
Similar proteins bind to same antibodies
Assessing Genetic Diversity
Comparing DNA sequences lets us know how many alleles of a gene are
present within the population
Various alleles make different mRNA sequences
Produces proteins with slightly altered amino acid sequences
Diversity, Classification and Variation
7
Biodiversity- Variety of organisms in area
Habitat- Location of organisms home
Community- Different populations for different species in a single habitat
Different Levels of Biodiversity
Local Biodiversity
Different species in a local habitat
Global Biodiversity
Total number of species on earth
Species Richness
Measure of biodiversity and number of different species in a community
by taking random samples in area
Diversity, Classification and Variation
8
Title: Diversity, Classification and Variation Summary
Description: Summary of topic 4B from A Level Biology AQA Revision book
Description: Summary of topic 4B from A Level Biology AQA Revision book