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Topic 5 – Evolution and Biodiversity
Evolution is the process of cumulative change in heritable characteristics of a population
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Heritable: passed down from one generation to the next

Evidence for Evolution
Fossils
Fossils show that life on earth is constantly changing
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Belgian Blues cows have been bred so they have more muscle so they will produce more meat
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The functions of the pentadactyl limb are walking, flying, swimming,
digging, jumping, and climbing
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Darwin explained this wasn’t a coincidence, it
was evidence to say they had a common ancestor
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Dark varieties of a typically
light variety of moths are
melanistic
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During
the industrial revolution
the trees started to get soot
on them, so the dark moths
became camouflaged and
the peppered moths died
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Topic 5 – Evolution and Biodiversity

Natural Selection
Causes of variation
Mutation – a change in the sequence of nucleotides or amount of DNA
Meiosis – crossing over
Fusion of gametes – during sexual reproduction
Environment – sunlight, soil nutrients, water, space
In most cases, it is a combination of genetic differences and the environment (nature vs nurture)
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It is influenced by the
environment, and there are a range of intermediate values between the two extremes, forming a
normal distribution curve
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Discontinuous Variation: controlled by a single pair of genes – one or a few variations
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Antibiotic Resistance in Bacteria
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Antibiotic resistance genes can be transferred to bacteria by a plasmid
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They spread from person to
person by cross-infection
The more antibiotics used, the more resistant the bacteria will be and there will be less nonresistant
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During droughts there are less small and
soft seeds available, but large and hard seeds are still produced
During droughts the population of finches with small beaks dropped from 1,300 to 300
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Coli and photosynthetic bacteria

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Topic 5 – Evolution and Biodiversity
Eubacteria – includes thermophiles and halophiles
Eukaryotes – includes animals, plants, and fungi
Archaea and eukaryotes are more closely related
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Hierarchical Classification:
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Groups are divided into more and more smaller groups
Organisms are classified on the basis of similar or shared features
There is no overlap between the groups

Kingdoms:
1
...

3
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5
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Phylogenetic classification takes into account the evolutionary history of an organism and forms
groupings based on this phylogeny
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Each phylum is subdivided into classes, which are a large group of
organisms that have several basic features in common
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The
members of the orders have features in common
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Families are divided into smaller groups called genera
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A species is a group of organisms
that can produce fertile offspring
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Byrophyta – includes plants of very short stature, such as mosses
Structures are similar to root hairs (rhizoids), but no root
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Spores are produced in capsule that develops at the end of a stalk
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Filicinophyta – includes ferns and horsetails
Roots, leaves, and short non-woody stems
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Vascular tissue present
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3
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Leaves narrow with thick, waxy cuticle,
and vascular tissue present
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Male cones produce pollen
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Angiospermophyta – includes all plants which make flowers and have seeds surrounded by a
fruit
Usually have roots, leaves, and stems
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Vascular tissue
present
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Fruits develop from ovaries to
disperse seeds

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Topic 5 – Evolution and Biodiversity
Animal Phyla
Invertebrates:
1
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Cnidaria (jellyfish)
Tentacles, stinging cells, mouth but no anus
3
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Annelida (worms)
Bristles often present, mouth and anus, segmented
5
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Arthropoda (spider)
Exoskeleton, joined appendages
Vertebrates:
7
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Bony ray-finned fish
Scales grow from the skin
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2
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External fertilisation in water and protective gel around eggs
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Reptiles (snakes)
Dry and scaly impermeable skin and lungs with extensive folding
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Birds
Feathers growing from skin and wings instead of front legs
5
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Dichotomous means each stage consists of a pair of
alternative characteristics
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Traits can be analogous or homologous
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They have a
different ancestry (convergent evolution)
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Homologous structures have a different function but are similar in fundamental structure
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Examples include the pentadactyl limb in vertebrates
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Evidence from cladistics has been used
to reclassify the figwort family according
to DNA evidence that has been
collected, which identified the different
common ancestors
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The general
flower shape and form of the seed
capsule evolved many times from
different ancestors
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