O’ Level Biology Notes
2020-01-27 Mr. F.Moyo - 0733214032
Topic 1 : Skeletal system
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Objectives
outline functions of the skeleton
identify the main bones of the fore & hind limb of a mammal
describe types of joints
describe the types of movement permitted by joints
describe the action of muscles at a hinge joint
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Functions of the skeleton
there are three types of skeletons
hydrostatic (liquid skeleton) e.g in worms
exoskeleton (outside hard layer) e.g insects /beetles
endoskeleton (inner bones) e.g humans
it performs three main (& two minor) functions :
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Functions of the skeleton
there are three types of skeletons
it performs three main (& two minor) functions :
protection
vital organs are enclosed or surrounded by
bones
organs like the brain, spinal cord,
heart,lungs are eyeballs are protected by
bones
movement
bones are moved by muscles which attach
to them
bones act as levers & joints act as pivots
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Functions of the skeleton
there are three types of skeletons
it performs three main (& two minor) functions :
support
bones of the vertebral column, pelvis & legs
support the body in its normal posture
production of cells
production of red & white blood cells occurs
in long bones, ribs, sternum & hip bones
storage
bones store minerals like calcium &
phosphorous
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Joints
- A joint is formed where two or more bones come together
Pivot joints:
Allow rotational movement, as when
you shake your head “no.”
Hinge joints
Allow movement in one plane,
like the bending of the elbow.
Ball-&-socket joints:
a Allow movement in several
planes, as when you move your
a Joints
hip.
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Joints
- A joint is formed where two or more bones come together
Pivot joints:
Allow rotational movement, as when
you shake your head “no.”
Hinge joints
Allow movement in one plane,
like the bending of the elbow.
Ball-&-socket joints:
a Allow movement in several
planes, as when you move your
a Joints
hip.
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Joints
- A joint is formed where two or more bones come together
Pivot joints:
Allow rotational movement, as when
you shake your head “no.”
Hinge joints
Allow movement in one plane,
like the bending of the elbow.
Ball-&-socket joints:
a Allow movement in several
planes, as when you move your
a Joints
hip.
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Joints
- A joint is formed where two or more bones come together
Pivot joints:
Allow rotational movement, as when
you shake your head “no.”
Hinge joints
Allow movement in one plane,
like the bending of the elbow.
Ball-&-socket joints:
a Allow movement in several
planes, as when you move your
a Joints
hip.
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Limbs
a a
a Upper limb a Lower limb
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Action of muscles
muscles consist of long slender cells called muscle fibres
muscle fibres are grouped in bundles & they are attached to
bones by tendons
they work by contracting & relaxing
when a muscle contracts, it becomes short & thick / fat
when a muscle relaxes, it becomes long & thin
muscles work by pulling bones & they work in pairs
two of muscles that cause opposite movements are called
antagonistic muscles
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Action of muscles
when bending an arm:
the biceps contract &
shorten
the triceps relax & return to
their length
the biceps pull on the radius
the arm bends at the elbow
a joint
a Flexor
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Action of muscles
when straightening an arm:
the triceps contract &
shorten
the biceps relax & return to
their length
the biceps pull on the ulna
the arm straightens
a Extensor
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Questions
1 The diagram shows three bones from the forelimb of a
mammal.
Between which parts is a ball and
socket joint formed?
A 1 and 3 B 1 and 5 C2
and 5 D 3 and 4
2 The diagrams show two stages in weightlifting.
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Questions
1 1 Muscles that move bones at joints are arranged in pairs.
1 State the term used to describe such a pair of muscles. [1]
2 Explain why muscles are arranged in this way. [3]
3 Name a muscle in the human body that is not arranged as one of a
pair. [1]
2 Name two different types of joint found in the arm. For each joint,
state exactly where in the arm it is found. [2]
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Answers
1 1 1 antagonistic;
2 one muscle contracts
while the other relaxes
3 muscles can only contract / only pull / never push
one muscle causes a change, the other restores the position
e.g. so the action can be reversed.
4 ciliary muscle / sphincter muscle or any named / heart / diaphragm;
2 hinge + elbow / position described
ball and socket + shoulder / position described;
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Topic 2 : Summary
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For Further Reading I
Gareth, Williams and Richard, Fosbery and Janet, Adams.
Biology for Cambridge IGCSE
Nelson Thornes, 2009.
Darwin, A and du Toit, L,
Focus on Science Book 3 Science Book.
College Press, 1995.
Jokomo Judith,
O’ Level Biology Today.
ZPH Publishers.
Avis, J and Baxter, F and Chavunduka, K.
Biology Step Ahead Book 4.
Pearson, 2017.
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For Further Reading II
Adam-day, Sam.
A Level Notes Water.
https://alevelnotes.com/notes/biology/biological-
molecules/biological-molecules/water,
2019-02-05.
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