reproduction Flashcards
(142 cards)
1
Q
what are the advantages of asexual reproduction?
A
- useful when the environment is stable
- completed much faster
- enables an organism to quickly populate
- more time + energy efficient
- if it’s well adapted to its environment, successful characteristics are carried on
2
Q
what are the disadvantages of asexual reproduction?
A
- disease likely to affect the whole population as there is no genetic variation
- population is only suited to one habitat
- population is vulnerable to changes in conditions
- limited genetic variation in population
3
Q
what are the two types of cell division?
A
mitosis and meiosis
4
Q
what is the use of meiosis?
A
to produce gametes for sexual reproduction
5
Q
what is the use of mitosis?
A
growth and repair
6
Q
how many daughter cells are made in mitosis?
A
two genetically identical daughter cells
7
Q
are offsprings from sexual reproduction genetically identical?
A
no, they are genetically different
8
Q
how many chromosomes do the daughter cells contain and why is this important?
A
- 23 (a haploid amount)
- important so zygote has correct number when gametes fuse
9
Q
how many daughter cells are produced in meiosis?
A
4 genetically different daughter cells
10
Q
how many cell divisions occur in mitosis and meiosis?
A
- 2 cell division in meiosis
- 1 cell division in mitosis
11
Q
how does sexual reproduction lead to variation in offspring?
A
there are two parent cells, so two sets of genetic information
12
Q
where does mitosis occur?
A
all body cells, except the gametes
13
Q
where does meiosis occur?
A
only in the gametes
14
Q
what is the function of the sepal?
A
to protect the unopened flower
15
Q
what is the function of the petal?
A
may be brightly coloured to attract insects
16
Q
what is the function of the stamen?
A
male part of the flower, comprising an anther attached to the filament
17
Q
what is the function of the anther?
A
produces the male sex cells (pollen)
18
Q
what is the function of the stigma?
A
the top of the female part go the flower, which collects pollen grains
19
Q
what is the function of the ovary (plants)?
A
produces the female sex cells (contained in the ovules)
20
Q
pollination definition.
A
pollination is the transfer from anther to stigma of a plant
21
Q
position of stamen in insect pollinated plants
A
enclosed so the insect has to make contact
22
Q
position of stamen in wind pollinated plants
A
exposed so pollen can easily blow away
23
Q
position of stigma in insect pollinated plants
A
enclosed so insect has to make contact
24
Q
position of stigma in wind pollinated plants
A
exposed to catch pollen blowing in the wind
25
type of stigma in insect pollinated plants
sticky so pollen grains can attach from insects
26
type of stigma in wind pollinated plants
feathery so it can catch pollen grains blown by
27
size of petals in insect pollinated plants
large and colourful to attract insects
28
size of petals in wind pollinated plants
small because it doesn't need to attract insects
29
colour of petals in insect pollinated plants
bright and colourful to attract insects
30
colour of petals in wind pollinated plants
dull, green mostly
31
nectary's in insect pollinated plants
present - they produce nectar, a sweet liquid containing sugars as a reward for insects
32
nectary's in wind pollinated plants
not present - don't need to attract insects
33
pollen grains in insect pollinated plants
sticky and large
34
pollen grains in wind pollinated plants
smaller, smooth, inflated grains to carry in the wind
35
what is self-pollination?
when pollen goes from the anther to the stigma of the same plants, this can result in a genetically weaker plant
36
what is cross-pollination
when pollen goes from one plant to another of the same type, this results in stronger plants
37
fertilisation definition
the fusion of gametes to form a zygote
38
the order of pollination and fertilisation in a plant.
1. a pollen grain on the stigma grows a tiny tube, all the way down the style to the ovary. (pollen tube releases digestive enzymes to digest way through tissue of style into ovary)
2. the pollen tube carries a male gamete to meet a female gamete in an ovule
3. the pollen tube curves around the ovule to enter the opening in an ovule
4. the tip of the tube dissolves and allows the pollen grain nucleus to move out of the tube and into the ovule
5. the nucleus of the pollen grain MUST fuse with the nucleus of the ovum for fertilisation to occur
6. the two gametes join and their chromosomes combine, so that the fertilised cell contains a normal complement of chromosomes, with some from each parent flower
7. after fertilisation, female parts of the flower develop into a fruit seed
8. the rest of the carpel becomes a fruit
39
name 4 methods of seed dispersal
1. wind dispersal
2. water dispersal
3. animal dispersal
4. bursting
40
what does a seed contain?
- a plant embryo
- root (radical)
- shoot (plumule)
- one or two seed leaves
- starch
41
what 3 factors are required for successful germination?
- water
- oxygen
- warmth
42
what are the male gametes called?
sperm cells
43
when are male gametes produced?
always, continuously from birth
44
where are the male gametes produced?
testes
45
function of the bladder
the body's urine storage tank
46
function of the sperm duct
sperm passes through and mixes with fluids containing nutrients
47
function of the testes
exocrine gland - produces sperm via meiosis
endocrine gland - produces testosterone
48
function of the seminal vesicle
produces a fluid which mixes with the sperm to form semen
49
function of the urethra
tube inside penis which carries urine/semen - contains ring of muscle which prevents them mixing
50
function of the penis
passes urine out of the body and passes semen into the vagina
51
function of the scrotum
pouch which holds the testes - must be held outside body as sperm production requires a lower temperature of 35 degrees
52
function of the prostate gland
produces seminal fluid
53
what are the female gametes called
egg cell
54
where are the female gametes released from?
ovary
55
function of the fallopian tube
connects the ovary to the uterus, lined with cilia that waft the egg along and into uterus, site of fertilisation
56
function of the uterus
a muscular bag with soft lining, where foetus develops until birth
57
function of the cervix
a ring of muscle - keeps foetus inside uterus
58
function of ovaries
have hundreds of undeveloped ova - one is released per month
59
function of the vagina
muscular tube that leads from the cervix to outside the body
60
what is the purpose of the villi in the placenta?
- increases surface area:volume
-> increases rate of diffusion
-> nutrients can be transported faster
61
why should the blood flow in opposite directions in the placenta?
- to stop it mixing
-> possibility of different blood types
-> the body will try fight the other blood type
- maintain concentration gradient across whole blood vessel
62
adaptations of the placenta
- large surface area with villi
- good blood supply -> maintain concentration gradient
- keeps harmful molecules out
63
where its produced and function of testosterone
testes - to produce sperm
64
where its produced and function of FSH
pituitary gland - stimulates egg development and ovulation
65
where its produced and function of oestrogen
ovaries - stimulates thickening of uterus lining
66
where its produced and function of LH
pituitary gland - surges to stimulate ovulation, causes egg to mature
67
where its produced and function of progesterone
ovaries - maintains uterus lining, stops production of FSH and LH
68
which hormones increase on day 4 of menstruation
FSH and ovulation
69
which hormones increase of day 14 of ovulation
LH and progesterone
70
how can plants reproduce asexually
BUDDING
- process in which a new plant grows out of the bud on the parent plant
RUNNERS
- grow side shoots called runners via mitosis
71
role of the amniotic fluid in protecting the foetus
- protects the foetus from jolts and bumps
- keeps temperature fairly constant
72
how is the foetus protected by amniotic fluid
- a membrane called amnion (amniotic sac) encloses the foetus
- this secretes a fluid called amniotic fluid
73
examples of asexual reproduction
- budding
- runners
-> plants grow side shoots called runners via mitosis
74
what are the benefits of gardeners using asexual reproduction
- more efficient
- can choose what characteristics they want
75
asexual reproduction:
- no specialised gametes
- no fertilisation
- produces genetically identical offspring
- new cells are produced by mitosis from just one cell in the adult organism
76
full number of chromosomes
46
diploid
77
half number of chromosomes
23
haploid
78
what must a cell do to divide via mitosis
- make a copy of each chromosome before it divides. it does this by DNA replication. each daughter cell will receive a copy of each chromosome when the cell divides
- divide in a way that each daughter cell receives one copy of every chromosome. so that both daughter cells contain all the genes
79
mitosis process:
1) DNA is found as chromosomes in the nucleus
2) chromosomes become visible as each chromosome is copied and joined together
3) the nuclear membrane disappears, and the chromosomes line up along the centre of the cell
4) chromosomes are pulled apart to opposite poles by contracting fibres
5) the nuclear membrane forms around each group of chromosomes and the cytoplasm divides
6) two genetically identical daughter cells are formed
80
what is mitosis useful for
growth and repair
replacing dead cells
81
stages of sexual reproduction:
- formation of gametes (sex cells)
-> stationary female games (ovum/ova)
-> mobile male gamete (sperm)
- the male gamete is transferred and fused to the female gamete
- sperm fuses with the ovum - fertilisation, to form a zygote
- the zygote cell then divides many times via mitosis to form all the cells of the new organism
- characteristics are a combination of both parents
- leads to genetic variation
82
when are gametes produced
when cells inside the sex organs divide by meiosis
83
what are the gametes in animals
ovum
sperm
84
what are the gametes in plants
pollen
ovule
85
number of parent cells needed for sexual reproduction
two
86
number of parent cells needed for asexual reproduction
one
87
88
meiosis:
- forms gametes
- daughter cells have half the number of chromosomes of the parent cell
- results in 4 haploid cells
- genetically different daughter cells
89
what two things must happen in meiosis
- each chromosome must be copied so there is enough genetic material to be shared between the four daughter cells
- it must divide twice, in such as way that each daughter cell recieves just 1 chromosome from each homologous pair
90
process of meiosis
- in a diploid parent cells, chromosomes makes identical copies of themselves
- similar chromosomes pair up
- sections of DNA get swapped -> crossing over -> increase genetically variation
- pairs of chromosomes divide
- fibres pull chromosomes
- chromosomes divide again
- produces 4 haploid daughter cells that are genetically different
91
how does genetic variation happen
the genetic information gets swapped
92
how does sexual reproduction lead to variation in offspring
there are 2 parent cells
-> different genetic information
93
how do plants reproduce sexually
- sex cells (gametes) are produced
-> male sex cells - pollen grains
-> female sex cells - ova/ovum
- the male sex cells must be transferred to the female sex cells - pollination
- following pollination, fertilisation takes place and the zygote formed develops into a seed
- the seed becomes enclosed in a fruit
- offspring are not genetically identical
94
what makes gametes different to normal cells
they have a haploid number of chromosomes
95
what are the male sex cells in plants and where are they produced
pollen grains
produced in the anther of the stamen
96
what are the female sex cells in plants and where are they produced
ovum
produced in the ovules in the ovaries
97
what does a fertilised ovule go on to form and what does it contain
goes on to form a seed, which contains a food store and an embryo that will later grow into a new plant
-> the ovary develops into a fruit to protect the seed
98
what four key changes happen in seed and fruit formation
1) zygote becomes an embryonic plant with a radicle and plumule
2) contents of ovule develop into food store for when the seed germinates
3) seed coat or testa form from the ovule wall
4) ovary wall becomes a fruit coat
99
what is the food store in a seed
a store of food for the young plants to use until it is large enough to make its own food
100
what does the embryo consist of in a seed
consists of young root and shoot which will develop into the adult plant
101
what is the seed coat
tough protective outer covering
102
during germination what happens to the food store fo starch
it is used up as it provides the nutrients allowing the radicle and plumule to grow
103
how does the plumule (shoot) grow during germination
grows upwards towards the light so that it can photosynthesise
104
how does the radicle (root) grow during germination
grows down into the soil, where they will absorb water and mineral ions
105
what is the seeds food store of starch broken down by
enzymes to provide glucose or aerobic respiration to allow the seed to germinate
106
why does germination require water
- to split/soften testa
- activates digestive enzymes
107
why does germination need oxygen
aerobic respiration -> releases more ATP
108
why does germination require warmth
optimum temp -> sufficient KE for collisions
109
what are seeds like after dispersal and what does this mean
- seeds are usually very dry after dispersal - only have 10% of water
-> this restricts a seeds metabolism so it remains alive but dormant
-> when a seed germinates, dormancy is broken
110
when is germination over
when the seedling can photosynthesise
111
journey of the sperm cell during sexual intercourse
- sperm travels through sperm duct and mixes with semen
- travels into the urethra and are released out the end of the penis
112
adaptations of sperm cell
- digestive enzymes in head to break down protein coat on egg -> acrosome contains enzymes
- streamline body to swim faster
- tail to swim faster
- lots of mitochondria -> more aerobic respiration -> more ATP released
- nucleus is a haploid
113
when are ova produced and for how long
produced before birth until puberty
114
describe the journey of the ovum once released
- released from ovaries once a month
- travels down fallopian tube
- finishes in uterus
115
adaptations of ovum
- very large
- once sperm has entered cytoplasm, the plasma membrane becomes in-penetrable to other sperm
116
what must happen once the sperm meets the ovum
its nucleus must enter the ovum and fuse with the ovums nucleus
117
how many chromosomes does the zygote formed have
diploid amount (46)
becuase the sperm and ovum are haploid
118
what does zygote cell do to form a new organism
divides by mitosis
119
what does fertilisation provide
genetic variation
120
what is fertilisation
fusion of female and male gametes
121
how do humans reproduce
sexually
122
what is fertilisation like in humans
internal
123
reproduction in humans:
- semen (containing sperm) is ejaculated out of the penis into the vagina during sexual intercourse
- the sperm begin to swim towards the fallopian tube
- if an ovum is present in the fallopian tubes, then it may be fertilised by the sperm
- the zygote formed from fertilisation will begin to develop into an embryo
- this will implant tin to the lining of the uterus
- the embryo will develop a placenta
- after 8 weeks the embryo is called a foetus
124
role of the placenta
- allows the embryo to obtain oxygen and nutrients (eg. glucose, amino acids, fatty acids) from the mothers blood
- allows the embryo to get rid of waste products such as CO2 and urea
- anchors the embryo to the uterus
- secretes female hormones (mainly progesterone) to maintain the pregnancy and prevent the embryo from aborting
125
what attaches the embryo to the placenta
the umbilical chord
126
there is no physical connection between the circulatory system of the embryo and its mother, so blood does not mix. how do materials pass from one to the other
diffusion
127
what is carried in the umbilical artery
deoxygenated blood and waste products from foetus to placenta
128
what is carried in the umbilical vein
oxygenated blood and nutrients from placenta to foetus
129
what encloses the foetus
a membrane called amnion (amniotic sac)
130
what does the amniotic sac secrete
a fluid called amniotic fluid
131
what is the role of amniotic fluid
- protects the foetus from jolts and bumps
- keeps the temperature fairly constant
-> has a high heat capacity so requires a lot of energy to move the temp either way
132
changes that will happen to both boys and girls during puberty
- growth
- acne
- hair growth
- body odour
- hair and skin get greasier
133
changes that will happen to boys during puberty
- voices get deeper
- shoulders broaden
- muscle growth increases
- sperm are produced
134
changes that will happen to girls during puberty
- menstruation starts
- hips widen
- eggs (ova) are released
- breasts enlarge
135
what are changes brought about in puberty caused by
hormones that are released by the pituitary gland
136
what is the menstrual cycle
a recurring process which takes around 28 days
137
what happens during the cycle
the lining of the uterus is prepared for pregnancy
if pregnancy does not happen, the lining is shed - menstruation (period)
138
what day of the cycle does fertilisation roughly occur
day 14
139
day 1 of cycle:
- bleeding starts as the lining of the uterus breaks down and passes out of the valine
- this is known as menstruation or having a period
140
day 4 of cycle:
- the uterus lining begins to build up again forming a spongy layer full of blood vessels
- FSH increases
- oestrogen increases
141
day 14 of cycle:
- an egg is released from ovaries
- the thick uterus lining is maintained ready for implantation of a fertilised egg
- LH increases
- progesterone increases
142
day 28 of cycle:
- if egg is not fertilised the whole cycle starts again
- progesterone decreases
