Reproduction Flashcards
what is fertilisation
the fusion of haploid male and female gametes, restoring the diploid number of chromosomes in the zygote which then undergoes cell division and develops into an embryo
What is the difference between asexual and sexual reproduction
- S = genetically varied offspring
A = genetically identical offspring
what does sexual reproduction involve
sexual reproduction involves the joining of two sex cells or gametes during fertilization
organisms produced by sexual reproduction have two parents and are genetically similar to both but not identical to either
what does asexual reproduction involve and produce
involves only one parent so there is no joining of sex cells during fertilisation
organisms produced are genetically identical to each other and their parent - they are clones
what are the three ways an organism can naturally asexually reproduce
- runners (a new plant is produced where the runner touches the ground)
- tubers (one plant can produce many tubers which can each grow many shoots which form new plants)
- bulbs
what is an artificial method of reproducing asexually
cuttings
a piece of the 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
where is the stamen in a wind pollinated plant and why
exposed outside of the petals - to release pollen grains easier
where is the stamen in an insect pollinated plant and why
enclosed within flower - so insects must make contact in order to get to the nectar
where is the stigma in a wind pollinated plant and what is it like. Why?
exposed and often feathery - forms a network to catch pollen grains drifting by
where is the stigma in an insect pollinated plant and what is it like. Why?
enclosed and sticky - pollen grains tick to it as insects brush past
what are the petals like in a wind pollinated plant
small and often green
what are the petals like in an insect pollinated plant
large and brightly coloured
what is the nectar like in a wind pollinated plant
absent
what is the nectar like in an insect pollinated plant
present - produce sugary fluid to attract insects
what is a stamen
the word for both the anther and the filament
what is the stigma
the top of the big green bit in the middle
what does the anther do
produces the male gametes which are contained in pollen grains
where are the female plant gametes produced and what are they called
in the ovule found in the ovary
egg cells/ova
what does the stigma do
collects pollen grains
what does the ovary do in a plant
produces the female sex cells (contained in the ovules)
advantages of sexual reproduction
- introduces variation into the population
- the species can adapt to new environments
- a disease is less likely to affect all the individuals in a population
disadvantages of sexual reproduction
- time and energy needed to find a mate
- not possible for an isolated individual
advantages of asexual reproduction
- population can increase rapidly
- genetic advantages can be passed down to offspring
disadvantages of asexual reproduction
- no variation in a population
- species may only be suited to one habitat
- disease may affect all the individuals in a population
where is the style on a plant
the long tube beneath the stigma and above the ovary
number of pollen grains in an insect pollinated plant and why
moderate - insects transfer pollen grains efficiently
number of pollen grains in a wind pollinated plant
large amounts - most pollen grains are not likely to be transferred to another flower
what are the 8 steps of fertilization starting with
- pollen grains are deposited onto the stigma
- pollen grains are deposited onto the stigma
- The pollen grain grows a pollen tube which grows down through the
style. - Enzymes are secreted at the tip of the tube which digest the tissues of the style.
- When the tube reaches an ovule the male gamete travels through the tube
entering the ovule through a small hole called the micropyle. - It then fuses with the female gamete (ovum) in the process of fertilisation.
- The fertilised ovum divides by mitosis to form the embryo
- The ovule develops into the seed.
- The ovary develops into the fruit
how do germinating seeds utilize food reserves until they are ready to photosynthesise
They therefore use their food stores using ENZYMES that break down their starch carbohydrate stores.
These are then used as a fuel in respiration to release energy.
what 3 things do germinated seeds need to grow and why
Oxygen - to aerobically respire
Warmth - optimum temperature for enzymes
Water - to activate the enzymes
what is the role of oestrogen and testosterone during puberty
To bring about changes that lead to sexual maturity
what hormone does the placenta secrete and why
progesterone to ensure the uterus lining remains thick and to prevent the embryo from aborting
what is the amnion and what does it do
a membrane - during pregnancy, it secretes a fluid called amniotic fluid
what does amniotic fluid do
it protects the embryo against jolts and bumps, drying out, and temperature fluctuation
what is a foetus
as the embryo develops it becomes more and more complex. when it looks human we call it a foetus
what does a placenta do
connected by an umbilical cord, it develops from the embryo.
The placenta:
- anchors the embryo in the uterus
- allows glucose, amino acids and salts to move to the embryo
- allows CO2 and urea to move to the mother
why is it important that the mother’s and the embryo’s blood streams don’t mix
- the mother’s blood pressure is much higher
- the mother’s blood has white blood cells and other chemicals that would see the foetal blood as foreign and attack it
where is FSH secreted from
the pituitary gland
what is the target tissue/organ of FSH
follicle in ovary
what are the roles of FSH
- follicle develops and ovum matures
where is oestrogen secreted from
the follicle in the ovary
what are the target tissues/organs of oestrogen
- pituitary gland
- uterus lining
what does oestrogen do
- inhibits FSH production (no other ovum is matured)
- stimulates LH production
- thickens the uterus lining
where is LH secreted from
pituitary pland
what does LH do
- follicle on ovary releases mature ovum into oviduct (ovulation)
- remnant of follicle becomes corpus luteum
what is the target tissue/organ of LH
- follicle in ovary
where is progesterone secreted from
ovary (corpus luteum)
what does progesterone do?
- maintains the thickness of the uterus lining
- FSH and LH inhibited (no further ovum is matured and released)
in what three ways are sperm cell adapted for their purpose
- tail (to swim)
- haploid nucleus (half num chromosomes)
- many mitochondria (energy)
describe an experiment to investigate the conditions needed for seed germination
Test tubes with seeds inside
- tube a - no warmth (fridge)
- tube b - no water
- tube c - oxygen absorber sodium pyrogallol is used with a bung
- tube d - no light (wrapping foil)
- tube e - control
what are the two types of cell division
- mitosis
- meiosis
summarise a division by mitosis
- produces two, genetically identical daughter cells
- involves one division
- produces diploid cells in humans
- keeps the same chromosome number
Summarise a cell division by meiosis
- produces four, genetically different daughter cells
- involves two cell divisions
- produces haploid cells
- halves the number of chromosomes
describe the purpose of mitosis
- generates all adult cells (except gametes) so used in growth and repair
- used for asexual reproduction and cloning
describe the purpose of meiosis
- only used to produce gametes
- used for sexual reproduction
where in plants and animals does mitosis occur
- all throughout the human body and plant
where in plants and animals does meiosis occur
- only in ovaries and testes
- only in ovaries and anthers
how many pairs of chromosomes are in a diploid cell
- 23 pairs so 46 chromosomes
what are the 5 steps of mitosis
- each chromosome doubles to form a copy of each
- these copies (chromatids) are joined together and a single point (the centromere)
- the nuclear membrane breaks down. the chromosomes line up across centre of cell, attached to special spindle fibres
- the chromatids are pulled apart and move to opposite ends of the cell
- the cytoplasm and cell membrane divides to form two identical cells
what cells are formed in meiosis and why are they different from other cells
- gametes
- they are haploid so only have 23 chromosomes
what are the 5 steps of meiosis
- the DNA doubles to form a copy of each chromosome. these copies (chromatids) are joined together at a single point (the centromere)
- the nuclear membrane breaks down. the homologous pairs of chromosomes join together
- the homologous pairs of chromosomes exchange sections of DNA then attach to spindle fibres in pairs at the centre of the cell
- the pairs are pulled apart and move to opposite ends of the cell. the cell divides
- THE WHOLE PROCESS REPEATS ONCE MORE
how does random fertilisation produces genetic variation of offspring
as each gamete has variation due to meiosis and the fusing of the egg and sperm is random
what is ovulation
when a matured ovum is released into the oviduct
what are three differences between prokaryotes and eukaryotes
eukaryotes:
- have a proper nucleus
- have organelles
- have more than one chromosome
- lack plasmids
converse for prokaryotes
give an example of a disease caused by a protoctist
- malaria caused by the protoctist: plasmodium
- dysentery caused by th protoctist: amoeba
why does ethanol turn cloudy when lipids are present
because a white emulsion forms
explain the role of fibre (mark scheme)
- aids in peristalsis
- in moving food along intestine
- because it is indigestible
discuss possible reasons why there is a decrease in the number of squirrels from 2010 to 2016
- increased predation
- disease
- migration
- human impact
- other species enter woods and feed on nuts
what is a catalyst (mark scheme)
a substance that speeds up chemical reactions
explain what is meant by metabolic
- reactions or processes in cells
explain why it is important that a control variable is kept the same
- so that only one variable is changed
- because the control variable also affects the (rate)
how does increasing temperature result in an increase in crop yield (mark scheme)
- for the optimum temperature for enzymes
- will increase the rate of photosynthesis
- because molecules will have increased kinetic energy
- for more glucose
explain why many farmers limit the amount of chemical fertilisers they use
- increased soil concentration reduces water potential of soil
- prevents water uptake
- so plants wilt
- leaching and washing into rivers
- causes eutrophication
- loss of aquatic life
- natural fertilisers exist
- can produce organic which can sell for more
