2- co-ordination and response and reproduction Flashcards
(149 cards)
1
Q
homeostasis
A
the control or regulation of the internal conditions of a cell or organism
2
Q
it is important for an organism to keep internal conditions within set limits to ensure
A
they stay healthy and maintain optimum conditions to allow the organism to function in response to internal and external changes, if these limits are exceeded the organisms may die
3
Q
homeostasis maintains optimal conditions for
A
enzyme action and all cell functions
4
Q
the core temperature for a human is
A
37 degrees c
5
Q
if human body temperature changes within 2 degrees it can be fatal because
A
the change would stop essential enzymes from functioning optimally
6
Q
body temperature is monitored and controlled by
A
the thermoregulatory centre in the base of the brain as blood passes through it
7
Q
the thermoregulatory centre contains
A
temperature receptors and sends nervous impulses to the thermoregulatory centre, the brain then coordinates a cooling or heating response depending on what is required
8
Q
the skin contains
A
temperature receptors and sends nervous impulses to the thermoregulatory centre and the brain then coordinates a cooling or heating response depending on what is required
9
Q
heat exchange occurs
A
at the body surface as this is where the blood comes into closest proximity to the environment
10
Q
one way to increase heat loss is
A
to supply the capillaries in the skin with a greater volume of blood which then loses heat to the environment via radiation
11
Q
arterioles have muscles in there walls that
A
can relax or contract to allow more or less blood to flow through them
12
Q
during vasodilation
A
the muscles in arterioles relax causing the arterioles near the skin to dilate and allowing more blood to flow through capillaries
13
Q
sweat is secreted
A
by sweat glands
14
Q
the hair erector muscles in the skin relax causing
A
the hairs to lie flat which stops them from forming an insulating layer by trapping air and allows air to circulate over skin and heat to leave by radiation
15
Q
one way to decrease heat loss is to
A
supply the capillaries inn the skin with a smaller volume of blood, minimising the loss of heat to the environment via radiation
16
Q
shivering is a
A
reflex action in response to a decrease in core body temperature. muscles contract in a rapid and regular manner. the metabolic reactions required to power this shivering generate sufficient heat to warm the blood and raise the core body temperature
17
Q
the nephrons of the kidneys contain structures called
A
tubules through which filtrate passes on its way to the bladder. water can be reabsorbed from this filtrate as it passes along these tubules. if the water content of the blood is too high then less water is reabsorbed but if it is too low then more water is reabsorbed
18
Q
the pituitary gland in the brain constantly releases a hormone called
A
ADH
19
Q
adh affects the
A
permeability of the collecting ducts to water
20
Q
the quantity of adh released depends on
A
how much water the kidneys need to reabsorb from the filtrate
21
Q
if the water content of the blood falls below a certain level-
A
the blood is too concentrated, receptors detect this and stimulate the pituitary gland to release more ADH, this causes the collecting ducts of the nephrons to become more permeable to water, this leads to more water being reabsorbed from the collecting ducts, the kidneys produce a smaller volume of urine that is more concentrated
22
Q
if the water content of the blood rises above a certain level
A
the blood is too dilute, receptors detect this and stimulate the pituitary glands to release less ADH, this causes the collecting ducts of the nephrons to become less permeable to water, this leads to less water being reabsorbed from the collecting ducts, the kidneys produce a larger volume of urine that is less concentrated
23
Q
homeostasis is under
A
involuntary control
24
Q
a stimulus
A
a change to the environment
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a receptor
receptor cells that detect stimuli
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a coordination centre
a place which receives and processes information from receptors
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effector
a muscle or gland which brings about responses to restore optimum levels
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plants need to be able to grow in response to
certain stimuli
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tropism
the directional growth responses in response to light and gravity
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phototropism
response to light
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geotropism
response to gravity
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if the growth is towards the stimulus
the tropism is positive
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if the growth is away from the stimulus
the tropism is negative
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as shoots grow upwards
away from gravity and towards light the shoots are a positive phototropic response and a negative geotropic response
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as roots grow downwards
into the soil and away from light and towards gravity, roots show a negative phototropic response and positive geotropic response
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plants produce plant growth regulators called
auxins to coordinate and control directional growth responses such as phototropism and geotropisms
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auxins are produced in
the tips of the shoots and the roots
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in the shoots auxins promote
cell elongation
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more auxin in shoots =
more cell elongation = more growth
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in the roots auxins
inhibit cell elongation
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more auxin in roots =
less cell elongation = less growth
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the distribution of auxin in the shoots is affected by
light and gravity whereas the distribution in the roots is primarily affected by gravity
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unequal distributions of auxins cause
unequal growth rates in plant roots and shoots
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two different control systems in humans are called
nervous system, hormonal system (endocrine)
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changes in our external environment or the internal environments of our body act as
stimuli- the nervous and hormonal systems coordinate a suitable response to these stimulis
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the nervous system response to stimuli
information is sent through the nervous system as electrical impulses- these are electrical signals that pass along nerve cells known as neurons, these impulses travel along neurones at very high speeds, this allows rapid responses to stimuli
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the endocrine system response to stimuli
information is sent through the endocrine system as chemical substances known as hormones. hormones are carried by the blood and can therefore circulate around the whole body. hormones transmit Information from one part of the organism to another and bring about a change. they alter the activity of one or more specific target organs
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hormones are used to control
functions that do not need instant responses
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central nervous system
the brain and spinal cord
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peripheral nervous system
all of the nerves of the body
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information is sent through the nervous system as
electrical impulses
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bundle of neurones is a
nerve
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the nerves spread out
from the central nervous system to all the other regions of the body as well as the sense organs
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the central nervous system acts as a
central coordinating centre for the impulses that come from or are sent out to any part of the body
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neurons have a
cell body where the nucleus and main organelles are found and cytoplasmic extensions from this body called axons and dendrites
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the axon is the
main long fibre of the neurone
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the axon is insulated by
a fatty myelin sheath with small uninsulated sections along its length called nodes- this means that electrical impulses don't travel down the whole axon, they jump from one node to the next
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many extensions called
dendrites extend out from the cell body of the neurone and at the far end of the axon- this means neurones can connect to many other neurones and receive impulses from them forming a network for easy communication
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main types of neurones
sensory neurones, relay neurones, moter neurones
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sensory neurones carry
impulses from sense organs to the central nervous system
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relay neurones are found in
inside the central nervous system and connect sensory and motor neurones
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moter neurones carry
impulses from the central nervous system to effectors
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sensory neurones are
long and have a cell body branching off the middle of the axon
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relay neurones are
short and have a small cell body at one end with many dendrites branching off it
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moter neurones are
long and have a large cell body at one end with long dendrites branching off it
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pathway of the nervous system
stimulus -> sensory neurone -> relay neurone -> moter neurone -> effector -> response
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describe the pathway of nervous system
first a stimulus is received by a sensory neurone, when a receptor is stimulated it produces electrical impulses. these impulses then travel along a sensory neurone to the central nervous system to either the brain or spinal chord. in the central nervous system the impulses are passed on to a relay neurone. the relay neurone links to the moter neurone along which the impulses travel until they reach the effector. the effector is what carries out the response
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neurones don't
come into direct contact with each other
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where the dendrites
of two neurones meet a junction known as a synapse is formed
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at a synapse
there is a very small gap between neurones- this gap is known as the synaptic cleft or synaptic gap
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electrical impulses can't
travel directly from one neurone to the next due to the synaptic cleft. instead the electrical signal is briefly converted to a chemical signal that can cross the synaptic cleft.
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the chemical signalling molecules used to transfer the signal between neurones at a synapse are known as
neurotransmitters
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once neurotransmitters cross the synaptic cleft and meet the neurone on the opposite side
the signal is converted back into an electrical impulse which can then pass along the neurone
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how an impulse is passed across a synapse
the electrical impulse travels along the first axon of the first neurone known as the presynaptic neurone. this triggers the end of the presynaptic neurone to release chemical messengers called neurotransmitters from vesicles. these vesicles fuse with the presynaptic membrane releasing their contents into the synaptic cleft. the neurotransmitters diffuse across the synaptic cleft and bind with receptor molecules on the membrane of the second neurone known as the postsynaptic membrane. this stimulates the second neurone to generate an electrical impulse which then travels down the second axon. the neurotransmitters are then destroyed to prevent continued stimulation of the second neurone. synapses ensure that impulses can only travel in one direction avoiding the confusion that would be caused within the nervous system if impulses were able to travel in both directions.
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a reflection response does not
involve the conscious part of the brain as a coordinator of the reaction
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a reflex arc is
the pathway of a reflex response, specifically the pathway taken by electrical impulses as they travel along neurones
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reflex response to pain
the object (stimulus) is detected by the pain/pressure/touch receptors in the skin. a sensory neurone sends electrical impulses to the spinal chord (the coordinator). an electrical impulse is passed to a relay neurone in the spinal chord and a relay neurone synapses with a moter neurone. a moter neurone carries an impulse to a muscle in the effector. when stimulated by the moter neurone the muscle will contract and pull the foot up and away from the object (response)
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the retina of the eye contains
two types of receptor cells- receptor cells that are sensitive to light known as rods and receptor cells that can detect colour known as cones
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cornea
transparent lens that refracts light as it enters the eye
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iris
controls how much light enters the pupil
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lens
transparent disc that can change shape to focus light onto the retina
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retina
contains light receptor- rods that detect light intensity and cones that detect colour
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optic nerve
sensory neurones that carry impulses between the eye and the brain
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pupil
hole that allows light to enter the eye
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the ciliary muscle
a ring of muscle that contracts and relaxes to change the shape of the lens
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the suspensory ligaments
ligaments that connect the ciliary muscles to the lens
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the sclera
the strong outer wall of the eyeball that helps to keep the eye in shape and provides a place of attatchment for the muscles that move the eye
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the fovea
a region of the retina with the highest density of cones where eyes see particularly good detail
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the aqueous humour
the watery liquid between the cornea and the lens
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the vitreous humour
the jelly like liquid filling the eyeball
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the choroid
a pigmented layer of tissue lining the inside of the sclera that prevents the reflection of light rays inside the eyeball
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the blind spot
the point at which the optic nerve leaves the eye where there are no receptor cells
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the eye when an object is close up
the ciliary muscles contract, this causes the suspensory ligaments to loosen, this stops the suspensory ligaments from pulling on the lens which allows the lens to become fatter and light is refracted more
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the eye when an object is far away
the ciliary muscles relax, this causes the suspensory ligaments to tighten, the suspensory ligaments pull on the lens causing it to become thinner and light is refracted less
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the eye responding to change in light intensity- dim light
photoreceptors detect change in environment (dark), radial muscles contract, circular muscles relax and the pupil dilates and more light enters the eye
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the eye responding to change in light intensity- bright light
photoreceptors detect a change in environment (bright), radial muscles relax, circular muscles contract and the pupil constricts and less light enters the eye
97
the skin is
our largest sense organ
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vasodilation of skin capillaries- inc heat
heat exchange occurs at the body surface as this is where the blood comes into closest proximity to the environment. one way to increase heat loss is to supply the capillaries in the skin with a greater volume of blood which then loses heat to the environment via radiation. arterioles have muscles in their walls that can relax or contract to allow more or less blood to flow through them. during vasodilation these muscles relax causing arterioles near the skin to dilate and allowing more blood to flow through capillaries
99
sweating
sweat is secreted by sweat glands, this cools the skin by evaporation which uses heat energy from the body to convert liquid water into water vapour
100
flattening of hairs
the hair erector muscles in the skin relax causing hair to lie flat, this stops them from forming an insulating layer by trapping air and allows air to circulate over skin and heat to leave by radiation
101
vasoconstriction of skin capillaries- decrease heat
one way to decrease heat loss is to supply the capillaries in the skin with a small volume of blood, minimising the loss of heat to the environment via radiation. during vasoconstriction the muscles in the arteriole walls con tract causing the arterioles near the skin to constrict and allowing less blood to flow through capillaries.
102
shivering
shivering is a reflex action in response to a decrease in core body temp. muscles contract in a rapid and regular manner. the metabolic reactions required to power this shivering generate sufficient heat to warm the blood and raise core body temperature
103
erection of hairs
the hair erector muscles in the skin contract causing hairs to stand on end. this forms an insulating layer over the skins surface by trapping air between the hairs and stops heat from being lost by radiation
104
information is sent through the endocrine system as
chemical substances known as hormones
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hormones are carried by
the blood and can circulate around the whole body
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hormones transmit information from
one part of the organism to another and bring about a change
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hormones are produced by
endocrine glands
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structures that make up the endocrine system
pituitary gland, thyroid, pancreas, adrenal glands, testes, ovaries
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pituitary glands
a master gland which makes hormones such as lh and fsh
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thyroid
produces thyroxine which controls metabolic rates and affects growth
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pancreas
produces insulin which regulates glucose levels
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adrenal glands
produces adrenaline
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testes
produces testosterone
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ovaries
produce oestrogen
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a hormone is
a chemical substance produced by a gland and carried by the blood which alters the activity of one or more specific target organs
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when is adrenaline produced
in situations where the body may be in danger
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what does adrenaline do
increases heat rate and breathing rate- ensures glucose and oxygen can be delivered to the muscle cells at a faster rate
diverting blood flow towards muscles and away from non essential parts of the body such as the alimentary canal- ensures an increased supply of glucose and oxygen (reactants of respiration)
dilation of blood vessels inside muscles- ensures more blood can circulate through them again, supplying more glucose and oxygen
breaking down of stored glycogen to glucose in the liver and muscle cells, with glucose released by the liver being transported to active muscle cells- ensures a higher blood glucose concentration for increased respiration in muscle cells (providing greater energy for movement)
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blood glucose concentration must
be kept within a narrow range so is another example of homeostasis- too high can lead to cells in the body losing water by osmosis, too low can can lead to the brain receiving insufficient glucose for respiration
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what controls blood glucose levels
the pancreas and liver
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how does the pancreas and liver control blood glucose levels
the pancreas acts as an endocrine gland, making and secreating hormones into the bloodstream)
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if blood glucose levels get too high-
cells in the pancreas detect the increased blood glucose levels, the pancreas produces the hormone insulin, secreating it in the blood. insulin stimulates muscles and the liver to take up glucose from the bloodstream and store it as glycogen. this reduces the concentration of glucose in the blood back to normal levels, at which point the pancreas stops recreating insulin
122
if the blood glucose levels get too low-
cells in the pancreas detect the decreased blood glucose levels. the pancreas produces the hormone glucagon. glucagon causes the glycogen stored in the liver to be converted into glucose and released into the blood. this increases the concentration of glucose in the blood back to normal levels, at which point the pancreas stops recreating glucagon
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testosterone
testosterone is produced in the male testes, it is responsible for the development of secondary sexual characteristics in males
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progesterone
progesterone is produced in the female ovaries. it is responsible for maintaining the uterine lining during pregnancy
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oestrogen
oestrogen is produced in the female ovaries, it is responsible for the development of secondary sexual characteristics in females and regulating the menstrual cycle
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sexual reproduction is
the process involving the fusion of the nuclei of two gametes to form a zygote and the production of a genetically different offspring
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fertilisation
fusion of a male and female gamete
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gamete
sex cell
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gamete animals
sperm and ovum
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gamete plants
pollen nucleus and ovum
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gametes contain
half the number of chromosomes found in other body cells- they have a haploid nucleus, this is because they only contain one copy of each chromosome rather than two copies found in other body cells
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a normal body contains how many chromosomes
46
133
each gamete has how many chromosomes
23
134
when male and female gametes fuse they become
a zygote
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zygote
fertilised egg cell
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zygotes have how many chromosomes
46
137
zygote nucleus is
diploid
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advantages of sexual reproduction
increases genetic variation, species can adapt to new environments due to variation giving them a survival advantage, disease is less likely got affect the population due to variation
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disadvantages of sexual reproduction
takes time and energy to find mates, difficult for isolated members of the species to reproduce
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asexual reproduction
the process resulting in genetically identical offspring being produced from one parent
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asexual reproduction does not
involve gametes or fertilisation
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how many parents required for asexual reproduction
1 so there's no fusion of gametes and no mixing of genetic information
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asexual reproduction offspring are
genetically identical to the parent and eachother
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plants reproduce by
asexual and sexual reproduction
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bacteria reproduce by
asexual reproduction called binary fission
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advantages of asexual reproduction
population can be increased rapidly when conditions are right, can exploit suitable environments quickly, more time and energy efficient, reproduction is completed much faster than sexual reproduction
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disadvantages of asexual reproduction
limited genetic variation, population vulnerable to changes in conditions and may only be suitable to one habitat, disease is likely to affect the whole population
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key differences between sexual and asexual reproduction
- number of parent organisms
- how offspring are produced
- level of genetic similarity between offspring
- possible sources of genetic variation
- number of offspring produced
- time taken to produce offspring
149
