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B1 Topic 1 Variation
Classification: This is organising living organisms into groups.

Scientists classify organisms into groups according to how closely related they are to each other.
Nowadays scientists look at characteristics of organisms and many more features to place them into groups, for
example the system scientists use nowadays…

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to classify animals into smaller groups. As the groups become smaller the animals in that group seem to have mo
and more characteristics.
Scientists find it hard to classify some animals into the animal groups which are mammals, reptiles, fish, birds and
amphibians. For example the duck billed platypus.


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produce hybrids. Also unrelated to the animal kingdom the definition of species is not always so clear cut
for example in plants and various fungi, different species can breed and produce fertile plants.

Ring Species

These are a group of related species that live in neighbouring areas, the species that…

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This type of variation can be any number within a certain range for example human heights they
range from a variety of numbers but all within a certain range, another example of continuous
variation is weight.

Discontinuous variation
This type of variation is when there are a fixed set of…

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Evolution means the gradual change over time.
Competition this is when there is only a limited amount of resources and the organisms have to compete to
get the resources.
Glossary definition: when organisms need the same resources as each other, they struggle against each
other to get those resources.…

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Gametes are the sex cells in plants and animals, the male gamete is called a sperm cell and the female
gamete is the egg cell. Gametes are different to other cells in the body as they only have one copy of a
Hence gametes only have one allele for…

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The genotype is the alleles in the organism and the phenotype is the characteristic of the organism or how it
looks. If both the alleles in an organism are the same we call them homozygous however if the organism
has different alleles they are heterozygous.

The genotypes produced can also…

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Homeostasis this is when your body maintains stable conditions in your body in order for certain chemical
processes to happen. In basic word homeostasis is maintaining a stable internal environment.

Osmoregulation this is maintaining or regulating the water level in your body, keeping a balance between
the amount of water…

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Neurotransmissions which are the travelling of these impulses
Dendron this is the ending of a branch in the neurone it connects to other neurones.
Axon This is where the electrical impulse is sent through.
Dendrites these are the endings of the branches of the Dendron and these receive the…

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Reflex arc Diagram then explain thoroughly.

A reflex arc is the connection between a
sensory neuron and a motor neuron often via a
relay neurone that allows reflex actions to

Hormones are produced and released by glands called endocrine glands. Hormones act as chemical
messengers travelling via blood.…


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