Reproduction Flashcards
what is asexual reproduction
a process resulting in the production of genetically identical offspring from one parent
what are the advantages of asexual reproduction
- population can be increased rapidly
- can exploit suitable environments quickly
- time and energy sufficient
- reproduction is completed much faster than sexual reproduction
what are the disadvantages of asexual reproduction
- limited genetic variation in population
- population is vulnerable to changes in conditions and may only be suited for one habitat
- disease is likely to affect the whole population as there is no genetic variation
what is 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
what is fertilisation
the fusion of the nuclei of gametes
what is the nuclei of gametes and zygote
haploid for gametes and diploid for zygote
advantages of sexual reproduction
- increases genetic variation
- species can adapt to new environments due to variation- a survival advantage
- disease is less likely to affect population due to variation
disadvantages of sexual reproduction
- takes time and energy to find males
- difficult for isolated members of the species to reproduce
parts of an insect- pollinated flower
sepals, petals, stamens, filaments, anthers, carpels, style, stigma, ovary and ovules
function of sepal
protects unopened flower
function of petals
brightly colored to attract insects
function of anthers
produces and releases the male sex cells (pollen)
function of filaments
holds anther in position
function of style
connects the stigma to the ovary
function of stigma
top of female part that collects pollen grains
function of ovary
produces the female sex cell
function of ovule
in the ovary and it contains the female sex cells
what is pollination
the transfer of a pollen grain from an anther to a stigma
what is 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
potential effects of self- pollination and cross-pollination on a population
cross- pollination improves genetic variation whereas self pollination reduces genetic variety of an offspring. This is negative because if environmental conditions change it is likely that any offspring will have adaptations that suit the new conditions well.
cross-pollination relies on pollinators whereas wind- pollinated plants do not
what is fertilisation
occurs when a pollen nucleus fuses with a nucleus in an ovule
structural adaptations of insect-pollinated
of pollen grains- moderate- insects transfer pollen grains efficiently with a high chance of successful pollination
petals- large and brightly coloured to attract insects
scent and nectar- present- makes insects visit flower and push stame to get to nectar
# of pollen grains- moderate- insects transfer pollen grains efficiently with a high chance of successful pollination
pollen grains- large, sticky/spiky to attach to insects and be carried away
Anthers- inside flower, stiff and firmly attached to brush against insects
Stigma- inside flower, sticky so pollen grains stick to it when insect brushes past
structural adaptations of wind- pollinated flowers
Petals- small and dull, often green or brown
Scent and nectar- absent- no need to waste energy producing these
# of pollen grains- large amounts- most pollen are not transferred to another flower
Pollen grains- smooth, small and light so they are easily blown by the wind
Anthers- outside flower, swinging loose on long filaments to release pollen grains easily
Stigma- outside flower, feathery to catch drifting pollen grains
describe the environmental conditions that affect germination of seeds
water- allows seed to swell up and the enzymes in the embryo to start working for growth
oxygen- so that energy can be released for germination
warmth- as temperature rises the reaction which take place are controlled by enzymes improve
describe the growth of the pollen tube and its entry into the ovule
- when the right kind of pollen lands on the stigma, a pollen tube is formed
- the nucleus ships down the tube as it grows down the style towards the ovary
- the ovary contains one or more ovules, which each contain and ovum with a female nucleus that a male pollen nucleus fuses with
- the nuclei join together therefore the ovule has been fertilised and a zygote has been formed
- the zygote will divide and eventually form a seed within the ovule
functions of the male reproductive system
Testes- produces sperm and produces testosterone
Scrotum- sac supporting the testes outside the body to ensure sperm are kept at temperature lower than body temperature
Sperm ducts- sperm passes through the sperm duct to be mixed with fluids produced by the glands before being passed into the urethra for ejaculation
Glands- produces fluid called semen that provide sperm cells with nutrients
Urethra- tube that can carry out semen or urine/ has ring of muscle in the urethra prevents urine and semen from mixing
Penis- allows semen to pass into the vagina of a woman during sexual intercourse
describe fertilisation in humans
the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell)
adaptive features of a sperm
- has flagellum to swim to egg
- lots of mitochondria to provide energy to reach the egg
- has acrosome in order to digest the egg membrane and penetrate the egg cell membrane
adaptive feature of egg cells
- cytoplasm contains food storages for early development of zygote
- jelly containing changes at fertilisation to not allow the entry of any more sperm
compare male and female gametes
size- the sperm is very small and the egg is large
structure- the sperm has a flagellum and head and the egg has a round cell and covered with jelly coating
motility- the sperm is capable of locomotion and the egg is not capable of locomotion
numbers- the sperm produced in high #’s and the egg thousands of immature eggs in each ovary/ each month
state fertilisation in early development
the zygote forms and embryo which is a ball of cells that implants into the lining of the uterus
functions of the placenta
- exchange of soluble materials such as foods (amino acids and glucose), wastes and oxygen
- physical attachment of the fetus to the wall of the uterus
- protection: 1. of fetus from mother’s immune system
2. against dangerous fluctuations in mother’s blood pressure - secretion of hormones which maintain the lining of the uterus as the corpus luteum, breaks down by 3rd month
functions of the umbilical cord
After 11 weeks, the embryo becomes a fetus, which is joined by the umbilical cord. The umbilical cord has 2 arteries and a vein. The artery take blood from the fetus into the placenta and vein returns the blood to the fetus.
what is a sexually transmitted infection
an infection that is transmitted through sexual contact
what is HIV
It is a Human Immunodeficiency virus is a pathogen that causes STI and this leads to the development of AIDS
Describe methods of transmission of HIV
- sharing needles
- blood transfusions
- mother to fetus through the placenta
- mother to baby via breastfeeding
functions of the female reproductive system
ovaries- contains ova which will mature and develop when hormones are released
oviduct- connects the ovary to the uterus and is lined with ciliated cells to push the released ovum down it, fertilisation happens here
uterus- muscular bag with a soft lining where the fertilised egg will be implanted to develop into a fetus
cervix- ring of muscle at the lower end of the uterus to keep developing fetus in place
vagina- muscular tube that leads to the inside of the woman’s body, where the male’s penis will enter during sex and sperm are deposited
explain ow the spread of STIs is controlled
- limiting the number of sexual partners an individual has
- not having unprotected sex, always use a condom
- getting tested
- education programmes
Oestrogen function during puberty
they are produced in the ovaries (also by the placenta)
- development of female secondary sexual characteristics, e.g. enlargement of breasts growth of pubic hair and armpit hair, widening of hips
oestrogen function from puberty onwards
- involved in monthly preparation of egg release via the menstrual cycle until menopause. Also roles during pregnancy
testosterone function during puberty
produced in testes.
- development of male secondary sexual characteristics, e.g. enlargement of testes and penis, growth of hair, e.g. in chest, face and pubic region, deepening of voice
steps of menstruation
- at the start of the cycle, the cycle has broken down (menstruation)
- the hormone FSH (follicle stimulating hormone) is released from the pituitary gland
- FSH causes the maturation of a follicle in the ovary. A follicle is fluid- filled sac which contains the developing ovum. FSH also stimulates the secretion of oestrogen
= oestrogen is produced in the ovary and stimulates the repair of the uterus lining so that it becomes thicker in preparation for implantation. Oestrogen also promotes the secretion of LH - when the follicle is mature, FSH and LH (luteinizing hormone) are secreted by the pituitary gland and stimulate the release of the ovum in the oviduct (ovulation)
- the remaining cells of the follicle (stimulated by LH) become the corpus leuteum in the ovary which secretes progesterone
- progesterone maintains the thickness of the uterus lining for implanta
testosterone function from puberty onwards
causes sperm production
what is the menstrual cycle
it controls the development of mature ova and prepares the lining of the uterus to receive an embryo. In females on ovum is produced approximately every 28 days
