biology notes on coordination and control
Coordination and Response
Nervous Control in Humans
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The nervous system consists of two parts:
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Central nervous system (CNS) consisting of the brain and spinal cord, which are the
areas of coordination
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Peripheral nervous system (PNS) made up of nerves and neurones, which
coordinate and regulate bodily functions.
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Involuntary actions: not under conscious control e.g. reflex action
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Voluntary actions: are done if we decide to carry them out
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Types of Neurons
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Nerve impulse: an electrical signal that passes along nerve cells called neurones
Motor Neurone:
Sensory Neurone:
Relay (connector) neurone:
Reflex arc
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A reflex action is an involuntary, quick action to respond to a stimulus, in order to protect
the body from danger
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E.g. quickly removing your hand from hot metal surface
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They involve three neurones: a sensory neurone, relay neurone and motor neurone.
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The gap between neurones is called a synapse.
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How the reflex arc works:
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A stimulus affects a receptor (cell or organ that converts a stimulus into an electrical
impulse)
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A sensory neurone carries impulse from the receptor to the CNS
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Connector/relay neurone carries impulse slowly (because it has no myelin sheath)
across the spinal chord
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Motor neurone carries impulse from the CNS to the effector
•
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Effector (either a muscle or a gland) carries out the response
Reflex action: means of automatically and rapidly integrating and coordinating stimuli with
the responses of effectors (muscles and glands)
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Synapses
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Synapse: a junction between two neurones, consisting of a gap across which impulses pass
by diffusion of a neurotransmitter
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Synaptic cleft: small gap between each pair of neurones
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Inside the neurones axom, there are 100s of tiny vacuoles (vessicles each contain a chemical
called neurotransmitter)
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When an impulse arrives, the vessicles move to the cell membrane and empty their content
into the synaptic cleft
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The neurotransmitter quickly diffuses across the tiny gap and attaches to receptor molecules
in the cell membrane of the relay neurone
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This can happen because the shape of the neurotransmitter molecules is complimentary to
the shape of the receptor molecule
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Many drugs e.g. heroin act upon synapses
Antagonistic Muscle
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A muscle that opposes the action of another; e.g. biceps and triceps are antagonistic
muscles or circular and radial muscles in the eye
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Agonist: a muscle that contracts while another relaxes; e.g. when bending the elbow, the
biceps are the agonist
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Antagonist: a muscle that relaxes while another contracts; e.g. when bending the elbow, the
triceps are the antagonist
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Sense organ: groups of receptor cells responding to specific stimuli: light, sound, touch,
temperature and chemicals.
The Eye
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The sense organ responsible for sight
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Cornea: refracts light
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Iris: controls how much light enters pupil
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Lens: focuses light onto retina
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Retina: contains light receptors, some sensitive to light of different colours
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Optic nerve: carries impulses to the brain
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Accomodation
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Adjusting for near and distant objects.
Near Object
Distant Object
Ciliary muscles contract
Ciliary muscles relax
Ligaments relax
Ligaments are tight
Lens becomes short and fat
Lens becomes long and thin
Pupil Reflex
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Adjusting for high and low light intensity
Low Light Intensity
High Light Intensity
Radial muscles (straight lines) contract and
become shorter to pull the pupil (black dot)
making it wider, to let more light enter, to form a
clear image on retina
Circular muscles (circular lines) contract
and become shorter to reduce the size of
the pupil to protect retina from
bleaching.
Rods and Cones
Rods
Cones
Provide low detail, black & white images, good
for seeing in low intensity light (at night).
Provide detailed, coloured images; they
work in high light intensity.
Packed most tightly around edge of retina so
you can see things most clearly when not
looking directly at them.
Most tightly packed at centre of retina, so
objects are seen most clearly when being
directly looked at.
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Fovea:
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Part of the retina where the receptor cells are pushed most closley together
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Where light is focused when you look straight at an object
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Hormones
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A chemical substance, produced by a gland, carried by the blood, which alters the activity of
one or more specific target organs and is then destroyed by the liver.
Adrenaline
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A hormone secreted by the adrenal gland.
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It increases pulse rate, makes the glycogen in muscles is converted to glucose and released
into blood, makes you breathe deeper and more rapidly, airways become wider, and makes
skin become pale as blood is diverted away.
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Increases blood glucose concentration for respiration.
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Adrenaline is secreted for example: while bungee jumping or riding a rollercoaster
Gland
Hormone
Function
Adrenal gland
Adrenaline
Prepares body for vigorous action
Pancreas
Insulin
Reduces conc. of glucose in blood
Testis
Testosterone
Causes development of male sexual characteristics
Ovary
Oestrogen
Causes development of female sexual characteristics
Nervous and Hormonal Systems
Comparison
Nervous system
Endocrine system
Speed of action
Very rapid
Can be slow
Comparison
Nervous system
Endocrine system
Nature of message
Electrical impulses,
travelling along nerves
Chemical messenger (hormones)
travelling in bloodstream
Duration of response
Usually within seconds
May take years (puberty)
Area of response
Localized response (only
one area usually)
Widespread response (in many
organs)
Example of process
controlled
Reflexes such as blinking
Development of reproductive system
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Hormones are used in food production, for example oestrogen is used to boost growth rate
of chickens.
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Advantage: chickens grow quickly meaning more profit.
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Disadvantages: this may cause human males to develop feminine characteristics, and it is
unnatural.
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Homeostasis
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The maintenance of a constant internal environment.
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Homeostasis is the control of internal conditions within set limits
Negative Feedback
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Feedback controls the production of hormones – the hormones regulate their own
production.
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A negative feedback control is when the change in hormone level acts as a signal to cancel
out that change, so when blood hormone level is low, hormone production is stimulated,
when it is high, it is inhibited.
Glucoregulation
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Blood glucose levels are monitored and controlled by the pancreas
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The pancreas produces and releases different hormones depending on the blood glucose
level
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Insulin is released when blood glucose levels are high – the liver stores excess glucose as
glycogen
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Glucagon is released when blood glucose levels are low – the liver converts stored glycogen
into glucose and releases it into the blood
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When the control of blood glucose does not work, a person is said to have diabetes
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Type 1 diabetes is caused by the death of the cells that secrete insulin
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Symptom: hyperglycaemia (feel unwell, dry mouth, blurred vision and feel thirsty) or
hypoglycaemia (tired, show confusion and irrational behaviour)
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Treatment: eating little and often and avoiding large amount of carbohydrates,
injecting insulin to reduce blood glucose concentration
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Thermoregulation
Constant body temperature is maintained by:
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Insulation: provided by fatty tissue retains heat. Hairs become erect to trap warm air by
contracting erector muscles and vice versa.
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Vasodilatation: when it is hot, arterioles, which supply blood to the skin-surface capillaries,
dilate (become wider) to allow more blood near to skin surface to increase heat loss (face
redder)
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Vasoconstriction: when it is cold, arterioles, which supply blood to the skin-surface
capillaries, constrict (become smaller) to allow less blood near to skin surface to decrease
heat loss
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Sweating: the water evaporates giving a cooling effect
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Skin receptors: sense heat and sensory neurons send impulses to the hypothalamus
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Shivering: muscular activity generates heat
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Thermoregulatory centre: in the hypothalamus, it controls the use of corrective
mechanisms (e.g. sweating and shivering).
Homeostatic Organs
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Cells: change composition of blood as they remove nutrients and O2 and add wastes and
CO2
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Heart: keeps blood pressure constant to deliver oxygen and nutrients around body
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Skin: to maintain heat exchange with external environment
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Kidneys: regulate water and salt levels (osmoregulation) and the removal of wastes like urea
(excretion)
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Lungs: regulate gas exchange
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Intestines: supply soluble nutrients and water to blood
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Liver: regulates blood solutes and removes toxins
Tropic Responses
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Auxin:
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Plant hormones or growth substances
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Controls tropisms
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It is produced by cells at the tip of roots and shoots of plants
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Gravitropism: a response in which a plant grows towards (positive) or away (negative) from
gravity.
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Auxins’ role in gravitropism:
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Tend to settle at the bottom end of the root.
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However, this does not make the cells of the tip of the root grow longer; auxins
prevent cells at bottom tip of root from growing, making cells at top of root grow
faster.
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When cells of top of the root grow faster, they push root deeper into soil and root
gets longer.
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The root grows in direction of the gravitational pull.
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Phototropism: a response in which a plant grows towards (positive) or away (negative) from
the direction from which light is coming.
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Auxins’ role in phototropism:
•
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If sun shines on right side of a plant’s shoot, auxins will accumulate on dark opposite
left side.
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Auxins accumulating makes cells on left side grow faster than cells on right side.
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When left side of shoot starts growing faster than right side, shoot will start to bend
to right side towards sunlight.
Hormones can be used as weed killers: spraying with high concentrations of hormone (2,4D) upsets normal growth patterns. It affects different species differently so might only kill
one species not the other (this is good).
Drugs
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Drugs: Any substance taken into the body that modifies or affects chemical reactions in the
body.
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Antibiotics
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Antibiotics work by stopping a metabolic practice performed by the bacteria you are trying
to get rid of, but not performed by human cells.
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Some bacteria are resistant to antibiotics which reduces the effectiveness of antibiotics
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Development of resistant bacteria such as MRSA can be minimised by limiting use of
antibiotics only when essential and ensuring treatment is completed
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Antibiotics don’t work on viruses because they are not really living and they make the host
cell perform the tasks for them.
Heroin
Effects of the abuse of heroin: a powerful depressant
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Problems of addiction
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Severe withdrawal symptoms (vomiting, restlessness)
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Malnourishment as drug depresses appetite
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Financial problems – stealing, loss of job
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Infection from sharing needles e.g. HIV/AIDS
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Heroin affects the nervous system by its effect on the function of synapses
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Alcohol
Effects of excessive consumption of alcohol –a depressant:
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Causes coronary heart diseases
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Reduced self-control
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Depression
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Effect on reaction times
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Damage to liver – cirrhosis
Smoking
Some effects of tobacco smoke:
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Drying effect and heat irritate lungs – destroys cilia
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Nicotine is addictive, it is also a stimulant, it increases pulse rate and narrows blood vessels
which can cause damage
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Tobacco smoking can cause chronic obstructive pulmonary disease (COPD), lung cancer and
coronary heart disease
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Tar causes cancer, and is an irritant so causes coughing.
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There are other irritants in tobacco smoke including: smoke particles, ammonia, and sulphur
dioxide
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Emphysema: walls between alveoli break making large sacs, reducing surface area massively
and making you breathless after a couple of steps
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Loss of limbs due to poor circulation, CHD and lower sperm-count
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Carbon monoxide irreversibly bonds with haemoglobin which can lead to oxygen starvation
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Cancer of the stomach, pancreas and bladder etc.
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Liver is the site of breakdown of alcohol and other toxins
Hormones and Sports
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Hormones: can be used to improve sporting performance
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Testosterone
•
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Improved hand-eye coordination
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Improved body-fat composition
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Increased muscle mass
Anabolic Androgenic Steroids
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Affects limbic system
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Mood swings
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Impaired judgement
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High blood pressure
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Kidney failure
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Increased risks of prostate cancer (male)
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Inconsistencies of menstrual cycle (female)
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Changes in blood cholesterol
Reproduction
Asexual Reproduction
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The process resulting in the production of genetically identical offspring from one parent.
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Bacteria:
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•
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Reproduce by binary fission, each bacterium divides into two.
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The generation time is the time taken for a cell to divide into 2.
Fungi:
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Single-celled yeast reproduces by binary fission.
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All other fungi produce via spores.
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When the sporangium bursts it spreads the spores.
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Spores land and grow mycelium (roots) for example mushrooms
Potatoes:
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The shoot from a potato goes back underground and the stem swells to form a new
genetically identical potato.
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The swollen stem acts as a storage organ.
Advantages
Disadvantages
Fast: no need to find mate, fertilise etc.
No variation
Good characteristics are kept
Harmful genes transferred
Advantages
Disadvantages
Overcrowding- fighting for food
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Sexual Reproduction
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Sexual reproduction: process involving the fusion of the nuclei of two gametes (sex cells) to
form a zygote and the production of offspring that are genetically different from each other
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Fertilisation: the fusion of gamete nuclei
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Nuclei of gametes are haploid and that the nucleus of a zygote is diploid
Advantages
Disadavnatges
Produces genetically different
offspring
Takes lots of time and energy
don’t all die from change in the
environment
Good characteristics can be lost
Energy on improving appearances or pollen volume for
pollination (plants)
Sexual Reproduction in Plants
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Insect pollinated, dicotyledonous flowering plant: foxglove
Wind pollinated flower structure: grass
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Functions
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Sepal: protect the flower bud.
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Petal: brightly coloured and scented and may have nectarines which are all used to attract
insects, petals in wind pollinated flowers are tiny, and used for pushing the bracts (leaf-like
structures) apart to expose stamens and stigma
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Anther: has pollen sacs with pollen grains which contain the male nucleus (male gamete).
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Stigma: platform on which pollen grains land
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Ovary: hollow chamber, ovules grow from the walls.
Pollination
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Pollination: transfer of pollen grains from the male part of the plant (anther of stamen) to
the female part of the plant (stigma).
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Agents of pollination: insects, birds, mammals, water and wind
Insect Pollinated
Wind Pollinated
Large colourful petals – attract
Dull petals
Sweetly scented
No scent
Nectaries
No nectaries
Insect Pollinated
Wind Pollinated
Moderate amount of pollen
Huge amount of pollen
Pollen is spiky/sticky
Pollen round and smooth
Anther & stigma inside flower
Anther & stigma hangs out
Stick stigma
Stigma hairy
Flowers have stripes which act as guide-lines for insects
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Pollen tube: pollen grain lands on stigma and creates a tunnel down the style, through the
micropyle, to the ovules.
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Structure of non-endospermic seed:
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Formation of a seed: the zygote divides many times by mitosis to form and embryo. The
cotyledon is the food store. The testa stops drying out of embryo.
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Wind and animal dispersal are used by plants to colonise new areas; done because new
areas have less competition for light, space and nutrients, so seeds are more likely to
develop.
Wind Dispersed Seed
Animal Dispersed Seed
Dandelion
Apple (internal)
Wind Dispersed Seed
Animal Dispersed Seed
Sycamore
Bur (external)
Germination
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A process controlled by enzymes
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Water: activates enzymes to turn insoluble food stores into soluble substances, and makes
tissues swell so that the testa splits
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Oxygen: enters through the gaps in the testa (along with water), and is used in aerobic
respiration.
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Temperature: must be suitable for enzymes to work (at optimum temperature).
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Sexual Reproduction In Humans
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Male reproductive system:
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Testes: have many coiled tubes which produce sperm, and the cells between tubes produce
testosterone.
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Scrotum: holds testicles
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Sperm duct: carries sperm from testicles to urethra.
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Prostate gland: makes seminal fluid
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Urethra: carries semen from sperm duct to tip of penis
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Penis: male sex organ, used to transfer semen to the female.
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Female reproductive system:
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Ovary: contains follicles which develop into the ova and produces progesterone and
oestrogen
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Oviduct (fallopian tube): carries the ovum to uterus
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Uterus (womb): where the fetus develops.
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Cervix: neck of uterus: a strong rigid muscle, moist by mucus with a small opening
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Vagina: receives penis during intercourse, and way out for baby at birth. Moist tube of
muscle, flexible and secretes mucus
Menstrual Cycle
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•
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Day 1 to 5:
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In the ovary, FSH secreted by the Pituitary Gland to stimulate the maturation of
ONE follicle in the ovary.
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In the uterus: the endometrium breaks down; menstruation
Day 5 to 12:
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In the ovary the follicle keeps maturing
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In the uterus, oestrogen is secreted by follicle and the ovarian tissues to prepare
the endometrium
Day 13/14/15:
•
•
In the ovary, LH is also secreted by the Pituitary Gland to trigger the release of the
egg from follicle into the fallopian tube
Day 15 to 28:
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•
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In the ovary, LH triggers formation of Corpus Luteum
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In the uterus: progesterone is secreted by Corpus Luteum to
keep endometrium thick, waiting for possible embryo implant.
Day 28 – Scenario 1: Egg not fertilized
•
No implantation takes place, the Corpus Luteum degenerates, causing a lack of
progesterone.
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This means that endometrium is no longer thick, back to Day 1
Day 28 – Scenario 2: Egg is fertilized
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Implantation occurs.
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This makes the hormones to keep the Corpus Luteum maintained which means
that progesterone is high.
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This keeps the Endometrium thick for pregnancy
Hormones in Menstrual Cycle
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Oestrogen is secreted by the ovaries. It stops FSH being produced – so that only one egg
matures in a cycle and it stimulates the pituitary gland to release hormone LH.
•
Progesterone is a hormone secreted by ovaries. It maintains the lining of the uterus during
the middle part of the menstrual cycle and during pregnancy.
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Follicle stimulating hormone (FSH) is secreted by the pituitary gland. It causes an egg to
mature in an ovary and it stimulates ovaries to release hormone oestrogen
•
Luteinizing hormone (LH): is also secreted by pituitary gland and causes mature egg to be
released from ovary.
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Sexual Intercourse
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Penis fills with blood and becomes erect
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Vagina walls secrete a lubricant.
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Rubbing of the glans (end of penis) against the vagina wall sets of a reflex action, causes
sperm to be released from the testes, and is transported by peristalsis along sperm ducts
and urethra, where seminal fluid is added to make semen.
•
The exit of semen from the penis is called ejaculation.
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Sperm then swim through the cervix and oviducts to the first third of the oviduct (from the
ovary) where one combines with the egg.
Fertilization
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The fusion of an ovum and a sperm to form a zygote.
•
Development of zygote:
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One sperm penetrates
•
Ovum membrane alters to form barrier against sperm
•
Head of sperm (male nucleus) approaches and then fuses with the nucleus of the
ovum.
•
Zygote divides over and over, to make a ball of cells called an embryo.
•
It implants itself in the wall of the nucleus (implantation) which is followed by
conception
•
Development of foetus: zygote is changed through growth (mitosis) and development
(organization of cells into tissues and organs)
•
Umbilical cord: contains umbilical artery which carries deoxygenated blood and waste
products from foetus to placenta and umbilical vein which carries oxygenated blood and
soluble food from placenta to foetus. (Contains foetus’ blood)
•
Placenta: organ for exchange of soluble materials such as foods, wastes and oxygen
between mother and foetus; physical attachment between uterus and foetus. (Contains
mother’s blood)
•
Amniotic sac: membrane which encloses amniotic fluid, broken at birth.
•
Amniotic fluid: protects foetus against mechanical shock, drying out and temperature
fluctuations
Antenatal Care:
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Change in diet:
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More proteins → growth of foetus
•
Slightly more fat → the new cells’ cell membrane
•
More vitamin C and D → blood vessel walls and bones
•
Iron → haemoglobin
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Calcium → growth of bones and teeth
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Guidance on motherhood
•
Checks on foetus and mother including: weight check, blood tests, urine tests, blood
pressure checks, ultrasound scanning etc.
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Labour and Birth
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Labour: The uterine muscular wall contract and cervix tries to relax, then contractions get
more frequent. Contractions cause amniotic membrane to break and release amniotic fluid.
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Expulsion: Powerful Contraction pushes baby out.
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Afterbirth: Placenta is expulsed out. All contraction & pain gone
Gamete
Size
Mobility
Sperm
Smaller
Very mobile – use its tail
Number
Many more
(300,000,000)
Egg
Larger
Immobile – moved by peristalsis
Fewer and limited
| Damage beauty | | No additives /preservatives | | | Builds mother-child bond | | | No
cost/preparation | | | Causes decline in uterus size | |
Bottle feeding:
Advantages
Disadvantages
Less painful
More likely to develop illness
Other people can feed baby
Risk of wrong mixture
May contain supplement vitamins and minerals
Expensive
Sex Hormones
•
At puberty, the pituitary gland starts to stimulate the primary sex organs; the testes in males
and the ovaries in females.
•
Sex hormones – testosterone in males and oestrogen in females are released into the
bloodstream.
•
They only affect the target organs which have receptors which can recognize them.
•
Causes secondary sexual characteristics such as the growth of pubic hair and maturation of
sexual organs.
Methods of Birth Control
•
•
•
Natural:
•
Abstinence: don’t have sex
•
Rhythm method: don’t have sex during the fertile period, only during the safe period
Chemical:
•
Progesterone-only pill: pill which affects the uterus and makes implantation difficult
•
Spermicide: a chemical applied as a gel, cream or foam which kills sperm. It is very
unreliable on its own but makes barrier methods of contraception more effective.
Mechanical:
•
Condom: thin rubber covering over penis, it protects from impregnation and STDs,
used by man
•
•
Diaphragm: used by woman, prevent sperm entering uterus, reliable, must stay in
place 6 hours after sex, needs a correct size
•
Femidom: closed end, has a ring which gets pushed through cervix and open end’s
ring lies against the labia
•
IUD: plastic-coated copper coil, can be left inside for months or even years, has a
string which is used to remove it out of the vagina, reliable, it irritates uterus wall
preventing implantation
Surgical:
•
Vasectomy: sperm ducts are cut and tied
•
Female sterilization: oviducts are cut and tied
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Artificial Insemination
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By donor: man’s sperm has a problem, making impregnation impossible, so a donor gives his
sperm.
•
In vitro fertilization: an ovum is fertilized outside a woman’s body. The fertilized ovum is
implanted into the uterus.
•
Fertility drugs: drugs which enhance reproductive fertility. For women, fertility medication is
used to stimulate follicle development of the ovary. The side effect is multiple pregnancies.
They contain varying amount of FSH and LH.
Human Immunodeficiency Virus (HIV)
•
Transmission: Intercourse, blood transfusion, organ transplant or sharing needle with
infected person
•
Prevention:
•
•
Avoid intercourse with many partners
•
Use a condom
•
Don’t come in contact with other people’s blood
How it affects the immune system:
•
Infects and destroys lymphocytes
•
Decreases efficiency of immune system
•
Body becomes liable to infection by other pathogens
…
