3a - Reproduction Flashcards
What is the definition of fertilisation?
The fusion of Gamete nuclei
How many chromosomes in a gamete ?
23
What does a zygote have?
- 46 chromosomes (half from each parent)
- diploid nucleus
What are advantages to sexual reproduction?
- increases genetic variation
- species can adapt to new environments
- disease is less likely to have effect
What are disadvantages to sexual reproduction?
- takes time and energy to find mates
- difficult for those isolated to reproduce
What are advantages to Asexual reproduction?
- rapid population increase
- more time + energy efficient
What are disadvantages to Asexual reproduction?
- limited genetic variation
- population vulnerable to disease + change in conditions
What is the function of the sepal ?
Protects unopened flower
What is the function of the petals ?
Brightly coloured to attract insects
What is the function of the anther ?
Produces and releases pollen
What is the function of the stigma ?
Collects pollen grains
What is the function of the ovary (plants) ?
Produces the female sex cell
What is the function of the ovule ?
Contains the female sex cells
What is the male sex cell in a plant ?
Pollen
What is the male part of the flower and what does it contain?
Stamen - contains anther + filament
What is the female part of the flower and what does it contain?
Carpel- contains stigma, style + ovary
What are the conditions required for germination?
moisture, oxygen, warmth
Describe insect pollination
- anthers from a flower deposit pollen onto the insect
- the insect then deposits that pollen onto the stigma of another flower
Describe wind pollination
- when ripe, the anthers open + shed pollen into air
- the pollen is blown by wind onto a flower
What are features of insect pollinated flowers?
- large bright coloured petals
- stigma + anther INSIDE flower
- larger sticky pollen grains
What are features of wind pollinated flowers?
- small dull petals
- anther + stigma OUTSIDE flower
- small light pollen grains
When does cross pollination occur?
When pollen from one plant is transferred to the stigma of another plant of the same species
What is self pollination?
When pollen from a flower lands on its own stigma or another flower on the same plant.
What does self pollination reduce?
The genetic variation of offspring
Describe the role of a pollen tube during fertilisation in a plant
- the nucleus inside the pollen grain moves down the tube as the tube grows down the style towards the ovary
- pollen nucleus fuses with ovum nucleus = fertilisation
What is germination ?
The start of growth in the seed
What does a seed contain?
The zygote which divides into cells which develop into the embryo plant
What structure surrounds an embryo (plants) ?
Cotyledons
What does the cotyledon contain ?
Food reserves which provide the seed with energy for germination
How long do the cotyledons provide for?
Until the plant can make its own food via photosynthesis
When does the seed coat (testa) split?
After taking in water
What happens when the seed coat (testa) splits?
The production of the plumule + radicle
What is the function of the prostate gland ?
Produces semen, which provides sperm cells with nutrients
What is the function of the prostate sperm duct?
Sperm passes through it to be mixed with other gland fluids
What is the function of the urethra?
Tube that carries out urine + semen
What is the function of the testis?
Produces sperm + testosterone
What is the function of the scrotum ?
Ensures sperm are kept at the right temperature
What is the function of the oviduct?
- connects ovary to the uterus
- lined with ciliated cells to push ovum down it
What is the function of the ovary?
Contains female gametes
What is the function of the uterus ?
Has soft lining for a foetus to develop
What is the function of the cervix?
Ring of muscle at uterus end to keep the foetus in place during pregnancy
What are the features of a sperm cell ?
- flagellum (tail)
- many mitochondria
- enzymes
What are the features of an egg cell? (humans)
- cytoplasm to provide energy
- jelly like coating
What is the function of the placenta?
Ensures materials can be exchanged between the blood of the mother + foetus
What is the function of the umbilical cord?
Joins the embryo’s blood supply to the placenta for exchange of materials
What is the function of Amniotic fluid?
protects the embryo during development by cushioning it from bumps
What does the mothers blood absorb?
The baby’s waste products eg CO2 + urea
How do most molecules move across the placenta ?
By diffusion
What does the placenta prevent?
Toxins and pathogens getting into the foetus’ blood
How is the placenta adapted for diffusion?
- large surface area
- Villi which increase the surface area
- rich supply of maternal blood vessels.
What are secondary sexual characteristics controlled by in females + males?
Females - oestrogen
Males - Testosterone
What are the effects of oestrogen in women?
- breasts develop
- menstrual cycle
- body hair
What are the effects of testosterone in men?
- facial + body hair grows
- voice breaks
- muscles develops
- testes start to produce sperm
When does ovulation occur?
About halfway through the menstrual cycle (day14)
What is menstruation caused by?
The breakdown of the lining of the uterus
What releases FSH?
Pituitary gland
What releases LH and when?
Pituitary gland when oestrogen levels have reached their peak
What does FSH cause?
- causes egg to start maturing in the ovary
- stimulates the ovaries to release oestrogen
What does LH cause?
Ovulation + stimulates the ovary to produce progesterone
When does progesterone start to rise?
After ovulation (day 14 onwards)
Why does progesterone start to rise?
To cause the uterus lining to thicken further
What happens when progesterone levels fall?
Uterus lining breaks down (menstruation)
When do oestrogen levels rise?
From day 1-14(peak)
What does the rise of oestrogen cause?
- uterus lining thickens
- egg matures
What does oestrogen do after ovulation ?
inhibits FSH + LH production
What hormones does the ovary produce?
Oestrogen + progesterone
