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Biology - all note flashcards > Reproduction and growth - 4th form > Flashcards

Reproduction and growth - 4th form Flashcards

1
Q

what do growth and reproduction require

A

cell division

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2
Q

why do chromosomes replicate before a cell divides

A

they are making an exact copy of themselves to double the amount of DNA in the cell

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3
Q

what is mitosis

A

this produces genetically identical daughter cells. these cells are diploid - they have one pair of each chromosome in each nucleus. (human diploid cells have 23 pairs of chromosomes - 46 in total) mitosis is used for growth, repair and asexual reproduction

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4
Q

what is mitosis used for

A

growth
repair
asexual reproduction

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5
Q

what is meiosis

A

this produces haploid gametes (sperm, eggs, pollen) which are not genetically identical. (human haploid cells have 23 chroosomes in total - unpaired) meiosis is only used to produce gametes for sexual reproduction

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6
Q

what is meiosis used for

A

produce gametes for sexual reproduction

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7
Q

what is a consequence of meiosis

A

every gamete produced is genetically different - it carries different alleles to every other gamete

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8
Q

how is variation in offspring produced

A

genetic variation in gamete cells produced by meiosis
random fertilisation of ova (egg cells) by male gametes

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9
Q

differences in the processes of mitosis and meiosis

A

mitosis:
-produces genetically identical daughter cells
- produces two cells
- involves one division
-produces diploid cells in humans
- keeps the same chromosome number

meiosis:
- produces genetically non-identical daughter cells
- produces four cells
- involves two cell divisions
- produces haploid cells in humans
- halves the number of chromosomes

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10
Q

differences in the roles of mitosis and meiosis

A

mitosis:
- generates all adult cells except gametes (growth & repair)
- occurs throughout the human body
- used for asexual reproduction (cloning)

meiosis:
- only used to produce gametes
- only occurs in ovary and testis
- only occurs in ovary and anther
- used for sexual reproduction

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11
Q

explain the process of mitosis

A

1- the cell grows
3- the DNA replicates (is copied) to form two copies of each chromosome. these copes (chromatids) are joined together at a single point (the centromere)
3- the nuclear membrane breaks down. the chromosomes line up across the centre of the cell, attached to special spindle fibres
4- the chromatids (copies of chromosomes) are pulled apart and move to opposite ends of the cell
5- the cytoplasm and cell membrane divides to form two identical cells

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12
Q

how are gametes different from other cells

A

they have half the normal number of chromosomes (they are haploid)

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13
Q

what does meiosis produce

A

four genetically different haploid cells

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14
Q

what type of division is meiosis

A

unlike mitosis, meiosis is a reduction division - the chromosome number is halved from diploid

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15
Q

what is a result of meiosis and fertilisation

A

the maternal and paternal chromosomes meet in different combinations in the zygotes. consequently the offspring will differ from their parents and from each other in a variety of ways

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16
Q

explain the process of meiosis

A

1- the parent cell grows
2- the DNA replicates (is copied) to form two copies of each chromosome. these copies (chromatids) are joined together at a single point (the centromere)
3- the nuclear membrane breaks down. the homologous pairs of chromosomes join together
4- the homologous pairs of chromosomes exchange sections of DNA. they then attach to the spindle fibres in pairs, at the centre of the cell.
5- the homologous pairs of chromosomes are pulled apart and move to opposite ends of the cell. the cell divides
6- the chromosomes line up along the centre of the cell, attached to the spindle fibres. the chromatids separate and move to opposite ends of the cell. each cell divides again

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17
Q

what moves sperm through water

A

the tail-like flagellum

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18
Q

how often and where are egg cells released

A

produced monthly from the ovaries

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19
Q

how do women have their eggs

A

they are born with all of their eggs

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20
Q

when do males start producing sperm

A

in puberty

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21
Q

give an example of external fertalisation

A

in fish, the females release their ova into the water and the sperm have to swim through the water to fertilise the ova. this kind of fertilisation takes place outside the body and is therefore called external fertilisation

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22
Q

give an example of internal fertilisation

A

male animals including birds and mammals, ejaculate their sperm in a special fluid called semen into the bodies of the females during sexual intercourse. internal fertilisation then takes place inside the female’s body. fertilisation is much more likely

once the sperm has reached the ovum, its nucleus must enter the ovum and fuse with the ovum nucleus

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23
Q

how many chromosomes does a normal human body have (with the exception of red blood cells and gametes)

A

46 chromosomes - these consist of 23 pairs of homologous chromosomes (contain the same genes)

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24
Q

how many chromosomes does the body cell get from the mother and father

A

a set of chromosomes (23) that originated from the organism’s father (sperm cell), and a set of chromosomes (23) that originated from the mother (egg cell or ovum). the cell therefore has two sets of chromosomes and is known as a diploid cell

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25
what are cells with half the genetic information called
haploid cells
26
what has occured when the haploid sperm and haploid egg fuse
we say that fertilisation has occurred to form a diploid cell
27
what is the first cell that is formed at fertilisation known as
the zygote
28
what is fertilisation
the fusion of haploid male and female gametes, restoring the diploid number of chromosomes in the zygote
29
what are the parts of the female reproductive system
ovary oviduct uterus cervix vagina
30
what is the ovary
where egg cells are formed by meiosis (in the follicle). produces the hormones oestrogen and progesterone
31
what is the oviduct
egg cells travel down this to the uterus. lined with cilia which move the cell. site of fertilisation
32
what is the uterus (womb)
a lining forms in the uterus, where the embryo will implant.the foetus develops in the uterus, which has a thick muscular wall. this contracts during labour
33
what is the cervix
narrow opening to the uterus. this dilates (widens) during labour, to allow the baby to be born
34
what is the vagina
muscular tube that leads from the cervix to the outside of the woman's body. a man's penis goes into the woman's vagina during sexual intercourse and the baby passes through the vagina when it is born
35
what are the parts of the male reproductive system
testes sperm duct seminal vesicles and prostate gland penis urethra
36
what are the testes
where sperm cells are formed by meiosis. produces the hormone testosterone
37
what is the sperm duct
maturing sperm are transported along this tube
38
what are the seminal vesicles and prostate gland
release liquids into the sperm duct, which mixes with the sperm cells to form semen. the liquid provides nutrients to the sperm
39
what is the penis
transports urine and semen out of the body. contains tissue which fills with blood to become erect; this helps to pass the semen out of the body and into the female's vagina during sexual intercourse
40
what is the urethra
tube inside the penis which can transport wither urine or semen
41
what happens to the sperm during sexual intercourse
sperm pass along the sperm duct and are mixed with a fluid from the seminal vesicles. this mixture called semen, is ejaculated into the vagina of the female out of the urethra. the sperm then begin to swim towards the oviducts (also known as the fallopian tubes)
42
what has to be present for fertilisation
if an ovum is present in the oviducts, then it may be fertilised by sperm introduced during intercourse
43
how does random fertilisation produce genetic variation of offspring
- each male ejaculate will contain millions of sperm cells. each of these sperm cells is genetically different due to the process that has created them - each female egg cell will also be genetically different to how it was created - the sperm cell that fertilises the egg is random - this 'randomness' causes variation in the genetics of the new offspring
44
what hormone does the placenta secrete
progesterone
45
why does the placenta secrete progesterone
to ensure the uterus lining remains thick, and prevent the embryo from aborting
46
during pregnancy what membrane encloses the developing embryo
the amnion
47
what fluid does the amnion release
amniotic fluid
48
what does amniotic fluid do
protects the developing embryo against jolts and bumps (mechanical shocks), drying out, and temperature fluctuations (due to waters high specific heat capacity)
49
what do we call the embryo when it looks human
a foetus
50
once the foetus is born what do we refer to it as
a baby
51
what develops from the embryo
a placenta, connected by the umbilical cord
52
what does the placenta do
anchors the embryo in the uterus
53
what does the placenta allow
- nutrients (such as glucose, amino acids and salts) and oxygen to move from the mother to the embryo - metabolic wastes - carbon dioxide and urea - to move from the embryo to the mother
54
how do the materials pass from the mother to the baby
by diffusion
55
why is there no physical connection between the circulatory systems of the embryo and its mother so the blood doesn't mix
- the mother's blood is much higher pressure than the fetal blood - the mother's blood has white blood cells and other chemicals that would see the fetal blood as foreign, and attack it
56
what hormone is involved in puberty in males
testosterone
57
what hormone is involved in puberty in females
oestrogen
58
what secondary sexual characteristics develop in boys during puberty
voice breaks sperm production begins shoulder broaden facial, armpit, body and pubic hair growth greater muscle development growth and development of genitalia possible mood swings and acne
59
what secondary sexual characteristics develop in girls during puberty
voice deepens, but doesn't break the menstrual cycle begins pelvis broadens in preparation for pregnancy and labour armpit and pubic hair growth muscle development and fat deposits on breasts, hips and thighs growth and development of genitalia possible mood swings and acne
60
how does the menstrual cycle begin
the breakdown and loss of the uterine lining - this is the woman's period
61
what does the pituitary gland do at the same time as the period
begins to produce increasing amounts of the hormone FSH
62
what does the hormone FSH do
tells the ovary to form a mature egg cell - a follicle develops with the maturing egg inside it. the follicle produces the hormone oestrogen
63
why does the lining of the uterus get repaired after menstruation and thicken
it is brought on by the hormone oestrogen
64
what happens as oestrogen levels rise
FSH production stops and LH production in the pituitary gland is triggered
65
what does LH do
stimulates ovulation - the release of the mature egg from the ovary
66
what happens after the egg is released
it travels down the oviduct (fallopian tube) to the uterus - it is in the oviduct that fertilisation may happen, if sexual intercourse has taken place
67
what structure does what is left of the follicle in the ovary form
a structure in the ovary called the corpus lutem.
68
what does the corpus lutem do
makes another hormone called progesterone. later on in pregnancy, the placenta secretes progesterone, taking over the role of the corpus lutem
69
what is the first sign that a woman is pregnant
when her monthly periods stop
70
what is the function of the menstrual cycle
is to control the development of the lining of the uterus (womb) so that if the ovum is fertilised, the lining will be thick and ready to receive the fertilised egg. if the egg is not fertilised, the lining of the uterus is lost from the woman's body as the flow of menstrual blood called a period
71
what are the four hormones that control the timing of the events in the menstrual cycle
FSH Oestrogen LH Progesterone
72
what gland is FSH secreted from
pituitary gland
73
what is the target organ/ tissue of FSH
follicle in the ovary
74
what is the effect of FSH
follicle develops and ovum matures (not released yet)
75
what gland is oestrogen secreted from
the ovary (follicle in the ovary)
76
what is the target organ/ tissue of oestrogen
pituitary gland uterus lining
77
what is the effect of oestrogen
inhibits FSH production (stops another ovum being matured) stimulates LH production thickens the uterus lining
78
what gland is LH secreted from
pituitary gland
79
what is the target organ/ tissue of LH
follicle in ovary
80
what is the effect of LH
ovulation - follicle on ovary releases mature ovum into oviduct remnant of follicle (on ovary) becomes corpus lutem
81
what gland is progesterone secreted from
ovary (corpus lutem)
82
what is the target organ/ tissue of LH
pituitary gland uterus lining
83
what is the effect of progesterone
FSH and LH inhibited (stops further ovum being matured and released) thickness of uterine lining maintained
84
what is reproduction
the ability of living organisms to produce offspring
85
what are the two types of reproduction
sexual reproduction asexual reproduction
86
what type of offspring does sexual reproduction produce
genetically varied offspring using specialised sex cells called gametes
87
when is sexual reproduction an advantage
in a changing environment or when there is threat of disease from pathogens
88
what three steps need to occur for a new plant to be produced by sexual reproduction
pollination fertilisation germination
89
what are the sexual organs of a flowering plant
it flowers - these are sites of pollination and fertilisation
90
what type of offspring does asexual reproduction produce
genetically identical offspring
91
what is not needed for asexual reproduction
gametes and there is only one parent involved
92
what are some of the natural methods of asexual reproduction
runners tubers bulbs
92
when is asexual reproduction an advantage
in a stable environment because it allows parent plants with advantageous adaptations to produce offspring with the same beneficial characteristics
93
what happens in the runners method
a new plant is produced where the runner touches the ground
94
what happens in the tubers method
swollen underground stems containing lots of stored food. one plant can produce many tubers which can each grow many shoots which form new plants
95
what is the bulbs method
underground buds with thick fleshy leaves containing stored food. a main shoot will grow out of the parent bulb and another will grow out of the side 'daughter' bulb, forming two plants
96
what is an artificial method to grow plants from
cuttings
97
what is the method of cuttings
a piece of a plant's stem, with a few leaves attached, is cut from a healthy plant. this is planted in damp compost, where it will grow roots and develop into a new plant
98
what are the three main functions of the sex organs - flowers
production of gametes sites of pollination and fertilisation sites of seed and fruit formation
99
what is pollen
the gamete produced in the anther which is part of the male part (stamen) of the flower
100
what is the ova
is the gamete produced in the ovules found in the ovary within the female part (carpel) of the flower
101
what is pollination
the transfer of pollen from the anther of one flower to the stigma of another flower on another plant is cross-pollination. self-pollination, when the pollen does not reach a different plant, is less commonly seen
102
what are the two types of pollination
insect wind
103
where is the stamen in insect pollinated flowers
enclosed within flower
104
where is the stamen in wind pollinated flowers
exposed outside of the petals
105
where is the stigma in insect pollinated flowers
enclosed within the flower and sticky
106
where is the stigma in wind pollinated flowers
exposed outside of the petals,often feathery
107
what are the petals like in insect pollinated flowers
large and brightly coloured
108
what are the petals like in wind pollinated flowers
small, usually green
109
are there nectaries in insect pollinated flowers
yes they are present - produce sugary fluid to attract insects
110
are there nectaries in wind pollinated flowers
no they are absent
111
what are the two types of gamete
a mobile male gamete (sperm and pollen) and a stationary female gamete (ovum)
112
what must the gametes do to form a single cell called a zygote
fuse (fertilisation)
113
what does the zygote do to form all the cells of the new organism
will divide many times by mitosis
114
explain the process of pollination
1- in plants pollen grains are deposited onto the stigma 2- the pollen grain normally grows a pollen tube which grows down through the style 3- enzymes are secreted at the tip of the tube which digest the tissues of the style 4- when the tube reaches an ovule the male gamete travels through the tube entering the ovule through a small hole called the micropyle 5- it then fuses with the female gamete (ovum) in the process of fertilisation 6- the fertilised ovum divides by mitosis to form the embryo 7- the ovule develops into the seed 8 the ovary develops into the fruit
115
explain fruit formation
1- the zygote develops into an embryonic plant with a small root (radicle) and shoot (plumule) 2- the other contents of the ovule develop into cottyledons which will be a food store for the young plant when it germinates 3- the ovule wall becomes the seed coat, or testa (the hard coating of a seed) 4- the ovary wall becomes a fruit coat
116
explain germination
- germinating seeds need a great deal of energy quickly - they therefore use their food stores using enzymes that break down carbohydrate stores - these are then used as a fuel in respiration to release energy - this occurs until the leaves are in a position to photosynthesise
117
what do plants need in order to germinate
oxygen - to aerobically respire warmth - optimum temperature for enzymes water - to activate the enzymes
118
explain what is in the tubes when investigating the conditions needed for germination
crest seeds are added to cotton wool in test tubes -tube A is out in a fridge (so there is no warmth) and the rest are kept on a windowsill -tube B has the cotton wool left dry (no water) - tube C has the cotton wool moistened with boiled water and an oxygen absorber such sodium pyrogallol is adden to remove the oxygen and a bung is put on top (no oxygen) -tube D has all the conditions present - the cotton wool is moist - tube E is wrapped in foil (no light) after two or three days check for germination - could combine class results and calculate a % germination or mean length of seed for each condition

Biology - all note flashcards (8 decks)

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