Biology WJEC BY2 Notes for 2.1 Evolution

Wjec BY2.1 Evolution

Biodiversity - a measure of the number of species on the planet. The number of
species per square kilometre increases as one move from the poles to the tropics.
Tropical rain forests and coral reefs are the most diverse habitats on the planet.

Reasons for decline in…

o Because only those individuals with beneficial alleles have a selective
advantage e.g. white fur in arctic

o Can withstand selection pressures i.e. a factor which increases the chances of
a beneficial allele being passed onto the next generation e.g. competition,
predation, disease

o These individuals then reproduce

o Offspring…

o Greater variation
o With a higher mean
o Because there is less competition for food (with other finches)
o Therefore there is a smaller selective pressure

Classification:

Helps understand relationships between ancestors


o Phylogenetics:

Based on Evolutionary History of the organisms

It shows the Ancestry of groups or Points…

Biochemical techniques

o Compare the sequence of bases in DNA of genes (DNA Fingerprinting) - the
more similar the sequence the more closely related the species *N.B. The
best/most accurate technique for establishing relatedness




DNA is most similar, so most

closely related




o Compare the sequence of amino acids in…

o Rattus norvegicus = Brown rat

o Rattus rattus = Black rat

Binomial system is used to avoid confusion of local common names and different
languages ­ uses the Latin name



Kingdom Animal




Phylum Chordata (Non-chordata)



Arthropods Annelids




Class Millipedes/ Spiders Insects Crustacea

Centipedes



Characteristics of the 5 Kingdoms (excluding…

Fungi Kingdom e.g. mushrooms, yeast
Eukaryotic cells
Made up of hyphae threads forming a mycelium
Cells have Chitin cell walls
Heterotrophic feeding (often saprophytic)
Reproduce using spores

Protoctist Kingdom e.g. slime moulds, algae
Eukaryotic cells
Unicellular organisms that are Heterotrophic or Autotrophic
Multicellular organisms are autotrophic (Seaweed)
No specialised structures…

o a hard outer exoskeleton made of chitin

o paired jointed legs

o an open circulatory system

o a cavity which surrounds the body organs called (haemocoel)



Two important evolutionary developments are:

o jointed legs - modified to perform a variety of functions, including walking, swimming,
jumping, feeding, reproduction and…

Reptiles- mainly terrestrial and have dry skin with scales. They have lungs. The eggs are
fertilised internally, covered with a shell and laid on land.

Birds- they can fly and have feathers. Forelegs develop as wings. They have lungs and their
eggs have hard shells.

Mammals- have skin with hair.…