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Biology 10 The human nervous system, Biology 14 variation and evolution,…
Biology 10 The human nervous system
10.1 principles of homeostatsis
Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes
homeostasis is important for maintaining optimal conditions for enzyme action and all cell functions
in the human body homeostasis includes control of blood glucose concentration, body temperature and water levels
the automatic control systems may involve nervous or chemical responses
all control systems include receptors, coordination centres and effectors
Receptors detect stimuli in the external or internal environment.the receptor cells may be part of the nervous or hormonal control system
coordination centres, which include the brain, spinal cord, and organs such as the pancreas
Effectors, which are usually muscles or glands that bring about a response to the stimulus
10.2 The structure and function of the human nervous system
The nervous system uses electrical impulses to enable you to react quickly to your surroundings and coordinate your behaviour
Cells called receptors detect stimuli (changes in the environment)
impulses from receptors pass along sensory neurons to the brain or spinal cord (CNS). The brain coordinates the response, and impulses are sent along motor neurons from the brain (CNS) to the effector organs
10.3 reflex actions
reflex actions are automatic and rapid and do not involve the conscious parts of the brain
reflexes involve sesory, relay, and motor neurons
reflex actions control everyday bodily functions, such as breathing and digestion, and help you to avoid danger
the main stages of a reflex arc are: stimulus -->
receptor --> sensory neuron --> relay neurone --> motor neurone --> effector --> response
10.4 The brain
the brain is made up of billions of interconnected neurons that control complex behaviour
It has different regions, for example the cerebral cortex, the cerebellum, and the medulla, each having different functions
10.5 the eye
the eye = sense organ. has receptors in the retina. receptors = sensitive to light intensity and colour
the tough outer sclera has transparent region at front called the cornea. it lets light in and changes direction of light to the retina
the muscular iris controls size of pupil and amount of light let in
ciliary muscles and sespensory ligaments change shape of lens to precisley focus light on to retina
optic nerve carries impulses from retina to brain
10.6 common problems of the eye
accomodation = process changing shape of lens to focus on close or far objects
focusing on close objects = ciliary muscles contract and suspensory ligaments loosen. Lens becomes thicker to change direction of light rays stronger
Biology 14 variation and evolution
14.1 Variation
Variation is the differences in the characteristics of individuals in a population
Variation may be due to differences in the genes inherited or the conditions in which organisms develop or a combination of both genes and the environment
14.2 Evolution by natural selection
the theory of evolution by natural selection states thal all species of living things have evolved from simple life forms that first developed over 3 billion years ago.
Mutations occur continuously. very rarely, a new mutation leads to a new phenotype. If the new phenotype is suited to an environmental change it can lead to a relatively rapid change in the species
If two populations of a species become so different that they can no longer interbreed to form fertile offspring, they have formed two new species
14.3 selective breeding
selective breeding is a process where humans breed plants and animals for desired characteristics
desired characteristics include disease resistance, increased fod production in animals and plants, domestic dogs with a gentle nature, and heavily scented flowers
proplems can occur with selective breeding, including defects in some animals due to lack of variation
14.4 genetic engineering
genes can be transphered to the cells of animals and plants at an early stage of their development so they develop desired characteristics
crops that have had their genes modified are known as genetically modified crops (GM). GM crops often have improved resistance to insect attack or herbicides and generally produce a higher yeild
14.5 cloning
Tissue culture is a modern technique for cloning plants. small groups of cells are taken from part of a plant to grow identical new plants. it is important for preserving rare plant species in nurseries as well as for commercial use.
taking cuttings is an older and simpler method of producing many identical new plants from a parent plant. it is widely used by gardeners
transplanting cloned embryos involves splitting apart cells from a developing animal embryo before they become speciallised and then transplanting the identical embryos into host mothers
Biology 11 Human reproduction
11.1
Biology
B15 Adaptaions, interdependence and competition
15.1 the importance of communities