16. Reproduction Flashcards
Describe asexual reproduction
a process resulting in the production of genetically
identical offspring from one parent
Describe sexual reproduction
a process involving the fusion of the nuclei of two gametes to form a zygote and the production of offspring that are genetically different from each other
Define fertilisation
the fusion of the nuclei of gametes
Are nuclei of gametes haploid or diploid?
haploid
Is the nucleus of a zygote haploid or diploid?
diploid
Function of the petal
attracts insects, birds or mammals to carry out pollination
Function of the sepals
protects the growing flower and helps it to stop it drying out
Function of the stamen
produces male gametes (pollen) and provides correct structures and conditions necessary for pollen transfer
Function of the filament
holds the anther in a position where it is able to transfer its pollen to an insect/mammal/bird
Function of the anther
produces pollen grains (contain plant’s male gametes)
Function of the carpel
produces female gametes + provides structures/conditions necessary for fertilisation
Function of the style
supports and presents stigma in position where it can receive pollen (from insect/bird/mammal)
Function of the stigma
traps pollen from other flowers
Function of the ovary
contains ovules (which contain female gametes) which develop into seeds after fertilisation
Function of the ovules
produces and contains female gametes, which upon fertilisation develop into seeds
Advantage of self pollination:
plants do not rely only on pollinators
Disadvantages of self pollination:
- reduces genetic variation within a population of plants
- reduces ability to of a population to respond to changes in environment (such as changes in climate or introduced diseases)
Advantages of cross pollination:
- genetic variation increases within a population of plants
- improves the ability of the population to respond to changes in the environment and to disease
Disadvantage of cross pollination:
- relies solely on insects (pollinators)
What are the advantages of asexual reproduction?
- only one parent needed
- no time and energy spent on finding mate
- reproduction occurs quickly
- less time and energy needed
- no genetic variation: crop farming
What are the disadvantages of asexual reproduction?
- no genetic variation - more susceptible to pathogens + vulnerable to environment changes
What are the advantages of sexual reproduction?
- genetic variation
- more resistant to environment
- farmers can perform selective breeding
What are the disadvantages of sexual reproduction?
- time and energy to find mate
- time and energy
- slower
- involves two parents
How many number of flowers/plants do wind pollinated and insect pollinated have?
wind pollinated: many small
insect pollinated: fewer, larger
What is the plant population growth pattern
in wind pollinated and insect pollinated flowers?
wind pollinated: dense population
insect pollinated: small groups
How are the petals in wind and insect pollinated flowers?
wind pollinated: dull and small
insect pollinated: bright large
What are two adaptations of an insect pollinated flower that a wind pollinated flower doesn’t have?
good scent and nectar
How are the pollen grains in wind pollinated flowers?
smooth, small, light, many
How are the pollen grains in insect pollinated flowers?
sticky, large, heavy, not many
How are the stamens in wind pollinated flowers?
pendulous, long filaments, exposed anthers
How are the stamens in insect pollinated flowers?
short filaments with enclosed anthers
How are the carpels/ovary in wind pollinated flowers?
exposed
How are the carpels/ovary in insect pollinated flowers?
enclosed
How is the stigma’s surface in wind pollinated flowers?
sticky, feathery, exposed
How is the stigma’s surface in insect pollinated flowers?
sticky, flat, enclosed
Describe pollination
the transfer of pollen
grains from an anther to a stigma
Describe self-pollination
the transfer of pollen grains from the anther of a flower to the stigma of the same flower or a different flower on the same plant
What is cross pollination?
the transfer of
pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species
What are the effects of SELF-POLLINATION on a population in terms of variety, capacity to respond to changes in environment + reliance on pollinators?
- fewer genetic variation
- lower capacity to respond to changes in environment
- relies less on pollinators
What are the effects of CROSS-POLLINATION on a population in terms of variety, capacity to respond to changes in environment + reliance on pollinators?
- more genetic variation
- higher capacity to respond to changes in environment
- relies a lot on pollinators
When does fertilisation occur in plants?
when a pollen nucleus fuses with a nucleus in an ovule
What are three factors needed for germination of seeds?
water, oxygen and a suitable temperature
What enzymes are used in germination and how?
amylase breaks down starch into glucose, which is to be used by the embryo to grow
Describe the growth of the pollen tube and its entry into the ovule.
- pollen lands on stigma and are recognised by the receptors on stigma surface
- pollen tube grows down the style towards ovary
- pollen tube penetrates wall of the ovary to reach the ovule
- sperm cell inside the pollen grain moves down pollen tube, reaching the ovule and they fuse to form a zygote (fertilisation)
- the petals, stamen and sepals wither and fall from flower
- ovary grows and matures into fresh fruit: fertilised ovule turns into seed of the fruit
Function of the testes
production of sperm cells (by meiosis) and testosterone
What is testosterone?
male hormone involved in primary: sperm production- and secondary: penis enlargement, deep voice, body hair, shoulder enlargement, “aggressiveness” (sexual male characteristics)
What is the function of the scrotum?
sac enclosing testes outside of the body - protection and to ensure a proper temperature in testicles (35-33 deg.C)
What is the function of the sperm duct:
sperm passes to urethra
What is the function of the prostate gland?
lubricating secretion for semen: releases fluid rich in sucrose (which sperm cells will use as a source of energy in aerobic respiration)
What is the function of the urethra?
releases urine from urinary bladder for excretion and during ejaculation releases semen
What is the function of the penis?
erectile tissue and spongey muscle that fills with blood when men is sexually aroused: penis becomes erect and can be inserted inside the vagina
What is the function of the ovaries?
production of egg/follicle cells by meiosis and oestrogen + progesterone
What is oestrogen?
female hormone involved in primary - follicle production - and secondary - breast development, hips enlargement, body hair and fat deposits develop (sexual female characteristics)
What is the function of the oviducts?
tube that moves follicle cells from the ovary towards the uterus using peristalsis and ciliated cells, usual site for fertilisation
What is the function of the uterus?
muscular organ where embryo implants, foetus grows and further contracts during birth/labour so baby is delivered
What is and what is the function of the cervix?
muscular opening for uterus
- dilates for birth,
- acts as a barrier against sperm cells,
- opens when a woman is ovulating so it increases chance of fertilisation
What is and what is the function of the vagina?
muscular tube where:
- blood is released out of the body during menstruation,
- semen is deposited during sexual intercourse,
- passageway of natural child birth
Describe fertilisation in humans
fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell)
How are sperm adapted to their function?
flagellum: important for movement
mitochondria: important for aerobic respiration to keep flagellum moving
enzymes in acrosome: break down jelly coat present in the egg
How is an egg cell adapted to its function?
- jelly coat: changes stiffness when sperm cell penetrates, avoiding penetration of other sperm cells, avoiding polyspermy
- energy stores in cytoplasm: allows egg to survive for several days + nourishes zygote if fertilisation occurs until it can implant in the wall of the uterus
Compare male and female gametes in terms of: size, mobility and numbers
Female: large cell size, doesn’t move (is moved), one per menstrual cycle
Male: small cell size, moves using flagellum, millions per ejaculation (live for up to 5 days)
What happens to the zygote in early development?
the zygote forms an embryo which is a ball of cells that implants into the lining of the uterus
State the functions of the umbilical cord.
- connects the foetus to the placenta
- contains blood vessels which transport nutrients, oxygen and waste products
State the functions of the placenta.
- respiration
- excretion
- nutrition
- immunity
- hormonal
What is the placenta?
a very thin membrane allowing diffusion to take place between maternal and baby blood ( there is very close contact between maternal and baby blood, but they don’t mix to avoid coagulation of different blood types)
Placenta: respiration
allows diffusion of oxygen from mother to foetus and CO2 from foetus to mother
Placenta: excretion
allows diffusion of waste products produced by the baby such as lactic acid, urea, and bicarbonates into mother’s blood
Placenta: nutrition
allows diffusion of glucose, vitamins, and minerals from mother to foetus
Placenta: immunity
mother’s antibodies pass to baby
Placenta: hormonal
placenta releases 3 hormones to maintain pregnancy (HCG, oestrogen and progesterone)
Describe the thickening (luteal) phase
corpus luteum releases progesterone causing endometrium to thicken for implantation
Describe the menstruation phase
lining sheds, FSH is released, stimulating growth and maturation of 1 egg
Describe the follicular phase
follicles grow and mature, oestrogen releases as response to FSH stimulus (positive feedback) causing endometrium to rebuild
Describe the ovulation phase
oestrogen stimulates release of LH from pituitary gland, causing release of egg into oviduct
Where are oestrogen and progesterone released from and what do they target?
released by ovary, targets the uterus lining
What is the role of FSH?
causes an egg in an ovary to mature
What is the role of LH?
stimulates the release of a mature egg
What is the role of oestrogen?
builds up lining after menstruation
What is the role of progesterone?
thickens uterus lining after ovulation
What happens to the corpus luteum if the egg IS NOT fertilised?
corpus luteum is degenerated therefore levels of progesterone fall, leading to menstruation
What happens to the corpus luteum if the egg IS fertilised?
blastocysts releases a hormone that stimulates maintenance of corpus luteum: therefore levels of progesterone are kept high during all pregnancy so endometrium doesn’t shed
What is an STI (sexually transmitted infection)?
an infection that is transmitted through sexual contact
What is HIV?
human immunodeficiency virus- a pathogen that causes an STI
What may HIV infection lead to?
AIDS
Describe the methods of transmission of HIV
- transmitted by direct contact with certain body fluids from an infected person: like blood, semen and vaginal fluid.
- can happen through: - unprotected sex,
- cuts and sores,
- using contaminated needles for injecting drugs,
- receiving blood transfusions,
- mother to child during childbirth/pregnancy/breast-feeding
How is the spread of STIs controlled?
using condoms
What is the amniotic sac?
thin sac that protects the developing fetus within the uterus
What is amniotic fluid?
fluid that surrounds + protects the developing fetus within the amniotic sac
True or false: No toxins or pathogens can pass across the placenta.
F - some pathogens and toxins can pass across the placenta and affect the fetus
Which hormone does FSH interact with?
FSH stimulates the ovary to secrete oestrogen
Which hormones does oestrogen interact with?
inhibits the release of FSH
stimulates the release of LH
Which hormones does progesterone interact with?
inhibits the release of FSH and LH
Give a summary of the menstrual cycle, mentioning hormones, uterus lining etc…
- start of menstrual cycle -progesterone level low, allows release of FSH
- as FSH levels rise, FSH causes an egg to mature, and stimulates release of oestrogen
- as oestrogen levels rise, it inhibits the release of FSH (prevents +1 egg maturing at a time)
- rising levels of oestrogen stimulate release of LH
- high levels of LH —> release of mature egg from its follicle (ovulation- around day 14)
- empty follicle becomes corpus luteum - produces progesterone
- progesterone inhibits release of FSH and LH
- high level of progesterone helps maintain lining of uterus
- if woman doesn’t become pregnant, falling levels of progesterone and oestrogen trigger menstruation
When does ovulation happen?
around day 14
