reproduction (topic 16) Flashcards
define assexual reproduction
a process resulting in the production of genetically identical offspring from one parent
outline process of assexual reproduction
1.bacteria dna copied
2. continued growth of cell
3.division of cell into two
name examples of organsims that reproduce assexually
bacteria, starfish, yeast, ferns, strawberry plants
what are advantages of assexual reproduction
only one parent needed (meaning faster, and saves energy)
quick reproduction
individuals offsprings are identical (good for crops, if they possess a desireable trait)
what are disadvtanges of assexual reproduction
produces identical offsprings, species is more vulnerable to changes in enviornment or diseases
define 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 are gametes
sex cells needed for sexual reproduction
sperm- male
egg- female
fertilisation
the fusion of the nuclei of
gametes
how do the nuclei of gametes compare to the nucleus of a zygote
gametes are haploid and zygotes are diploid
what is meant by diploid and haploid
diploid- Describes a nucleus containing two sets of chromosomes, for example in body cells. 46 chromosomes
haploid-Describes a nucleus containing a single set of unpaired chromosomes. 23 chromosomes
advantages of sexual reproduction
introduces variation, more resistant to changes in environment or to diseases
good for selective breeding
disadvantages of sexual reproduction
takes more time and energy to find a mate, more than one parent needed
much slower
pollination
The transfer of pollen grains from the anther to the stigma.
insect pollination what is meaning
Flowers that transfer their pollen by way of insect pollinators.
pollinators
Insects that transfer pollen from flower to flower in pollination.
name structures found in an insect pollinated flower
stigma, style, ovary, anther, filament, ovule, sepal, petal
stamen
male parts of the flower composed of anther and filament
to produce male gametes (pollen) and provide the correct structures and conditions necessary for the transfer of pollen
carpel
female parts of the flower composed of ovary style and stigma
sepal
green part at the top of the stem, protect the growing flower and help to stop it drying out
petal
bright coloured part, to attract insects, birds or mammals to carry out pollination
filament
stalk that supports anther, hold the anther in a position where it is able to transfer its pollen to an insect, mammal or bird
anther
powdery appearance, coloured, produce pollen grains, which contain the plant’s male gametes
stigma
usually green tallest part of the flower sticky and waxy layer, to trap pollen from other flowers
style
strucutre that supports stigma, above the ovary, to support and present the stigma in a position where it can receive pollen from an insect, bird or mammal
ovary
green, bulb-shaped part near the bottom of the flower, contains ovules (which contain the female gametes) which will develop into seeds after fertilisation
ovule
structure within the ovule, female gametes are produced and contained within the ovules. Upon fertilisation, these ovules will develop into seeds
pollination
the transfer of pollen
grains from an anther to a stigma
how is the pollen in insect pollinated flowers
spiky outer layer, larger, less pollen produced
how is the pollen in wind pollinated flowers
smooth, light, smaller, bigger production
self pollination
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
cross polliantion
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 advantgaes and disadvantages of self pollination
do not rely on pollinators, less energy needed, only one mate, less pollen lost however reduces variation (reducing ability to respond to changes in enviornment such as diseases)
what are advantgaes and disadvantages of cross pollination
variation increases, relies on pollinators, more energy needed, more than one mate, more pollen waisted, relies on polliantors
difference between petals of wind and insect pollianted flowers
wind- small, dull in colour, no need to attract insects,
insect- bright, large, attracts insects pollinators
difference between anthers of wind and insect pollianted flowers
wind- loosely attached and dangle outside the flower so its pollen can be blown easily by the wind
insect- located inside the flower to brush against insects
difference between stigma of wind and insect pollianted flowers
wind- loosely attached and dangle outside the flower so they can catch wind-borne pollen from other plants; often appear feathery
insect- located inside the flower to brush against insects
what is something that insect pollinated flowers must produce but wind doesnt
nectar, scent
when does fertilisation occur in plants
occurs when a pollen nucleus fuses with a nucleus in an ovule
describe what happens once a pollen grain is attached by the stigma
after pollination, pollen tube grows down style towards ovary, male gamete (sperm) move through this tube. it then reaches ovary and penetrates throguh reaching ovule, where fertilisation occurs nucleus of sperm cell fuses with nucleus of egg cell forming a zygote whcih will then develop into an embryo, eventually becoming a new plant
germination
The process, controlled by enzymes, in which the seed begins to develop into a new young plant.
what is needed for germination to occur
water, oxygen, suitable temp
reproductive system
The organ system found in animals that is responsible for producing sperm cells or egg cells, and for producing new individuals by sexual reproduction
what are the main structures in the male reproductive system
sperm duct, prostate gland, penis, urethra, testis, scrotum
function of testes
organ in which sperm cells and testosterone are produced
function of scrotum
sack of skin that contains the testes, helping to keep them at a slightly lower temperature than the rest of the body
function of prostate gland
secretes fluid that nourishes and protects the sperm; the mixture of liquid and sperm is known as semen
function of sperm duct
muscular tube that connects a testis to the urethra
function of urethra
tube that allows the passage of semen and urine through the centre of the penis
function of penis
during sexual intercourse, the penis is inserted into the vagina, allowing the sperm to transfer into the female reproductive system
mains structures in female reproductive system
ovary, oviduct, vagina, cervix, uterus
function of ovary
produces egg cells, and the hormones oestrogen and progesterone
function of oviduct
tube connecting an ovary to the uterus; fertilisation usually occurs here
function of uterus
organ in which the embryo develops
function of cervix
ring of muscle between the vagina and the uterus
function of vagina
elastic muscular canal through which the newborn passes during childbirth; during sexual intercourse, the male’s penis is inserted into the vagina
describe fertilisation (humans)
the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell)
what are some adaptations of the sperm cell
tip of head has acrosome- secretes digestive enzymes allows sperm to pass through jelly coating on surface of an egg cell
flagellum- tail, allows movement
midpiece contains mitochondria- organelles release energy by respiration, which is needed to keep the flagellum moving.
what are some adaptive features of the egg cell
cytoplasm contains energy stores- allow the egg to survive for several days and to nourish the zygote if fertilisation occurs, until it can implant in the wall of the uterus.
jelly coat around the egg- allows sperm to aattach, hardens to prevent polyspermy, more than one sperm fertilisation
Compare male and female gametes in terms of:
size, structure, motility and numbers
male- much smaller, billions per ejaculation, move on their own
female- much larger, one released per month, cant move by their own
what happens in early developments after fertilisation has occurred
zygote forms an embryo which is a ball of cells that implants into the lining of the uterus
after eight weeks of development what is the embryo called
fetus
amniotic sac
fetus is surrounded by a protectivelayer called the amniotic sac, A thin sac that protects the developing fetus within the uterus.
amniotic fluid
The fluid that surrounds and protects the developing fetus within the amniotic sac. also contains nutrients needed bynthe fetus
placenta
An organ that develops in your uterus during pregnancy, providing oxygen and nutrients and removing waste products from the developing fetus.
main function of placenta
transport nutrients from mother to foetus
transport waste materials from foetus to mother
umbilical cord
A cord which connects the fetus to the placenta and contains blood vessels which transport nutrients, oxygen and waste products.
what does the placenta provide the foetus with
oxygen, carbohydrates, proteins, fats, vitamins, minerals and water it needs to grow
what does the placenta receive from the foetus
waste materials such as carbon dioxide and urea
how do these substances/ nutrients move from mother to foetus
The blood supply of the mother does not meet the blood supply of the fetus. Instead, substances diffuse through blood capillaries between the placenta and umbilical cord
describe function of placenta in terms of protection
mother’s blood does not physically mix with the fetal blood supply, the placenta provides a barrier to many of the toxins and pathogens to which the mother is exposed
what are some toxins which are able to diffuse through the placenta
nicotine, some pathogens eg. rubella virus
hormone
A substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs.
what are the two main hormones involved in puberty
testesterone- male
oestrogen- female
what are some roles of oestrogen in secondary sexual characteristics
breasts develop, hair under arms, hip bones wider, pubic hairs
what are some roles of testesterone in secondary sexual characteristics
facial hair, shoulders widen, hair under arms, penis and testes grow, voice deepens
menstrual cycle
The monthly cycle in which an egg is released from the ovaries, and the lining of the uterus prepares for the possible implantation of a fertilised egg. If implantation does not happen, the lining breaks down and is discharged from the body, along with the unfertilised egg.
ovulation
The release of a mature egg (ovum) from an ovary; it occurs approximately once every 28 days in humans. usually around day 14
what does the follicle develop into after ovulation
corpus luteum
what happens from day 4 in a menstrual cycle to the lining of the uterus
the lining thickens so that the egg cell after fertilisatio can implant itself, if egg not fertilised lining breaks down again= menstruation
menstruation
The process which involves the discharge of the uterine lining at the start of the menstrual cycle when an egg cell is not fertilised and it does not implant in the uterine lining. Often referred to as a period.
what are the 4 hormones involved in the control of the menstrual cycle and pregnancy
fsh, lh, progesterone, oestrogen
where is progesterone and oestrogen produced
both in the ovary, however progesterone by corpus luteum in the ovary
where is lh and fsh produced
in the pituitary gland
describe the menstrual cycle in terms of hormone action
1.level of progesterone low inhibit releason of FSH
2.levels of FSH rise, causes an egg to mature, stimulates releasion of oestrogen (re builds uterus lining)
3.levels of oestrogen rise, inhibts releasion of FSH, preventing more than one egg maturing at a time
4.oestrogen stimulates releasion of LH which stimulates the releasing of the maturest egg from its follicle into oviduct
5.empty follicle, becomes corpus lutheum, releases progesterone, inhibits releasion of FSH and LH
6.progesterone thickens the uterus lining, if women does not become fertilised, levels of progesterone fall, inhibiting menstruation to occur
what happens if women becomes pregnant in terms of hormones
corpous luteum continues to release oestrogen and progesterone
which later placenta controls production of these hormones
ensuring that:
-no more eggs are released from the ovaries
-maintain a thick uterine lining to support the growing fetus
-prevent the muscles of the uterus contracting, which would cause the early delivery of a premature baby.
sti
sexually transmitted infection, An infection that is transmitted via body fluids through sexual contact. can be caused by both virsues or bacterias
how is the spread of STI’s controlled
avoid sexual contact or use protection
limiting number of sexual partners
being tested for an sti
what is HIV
a pathogen that causes an sti
human immunodeficiency virus
can lead to aids
only transmitted through direct contact with certain bodily fluids eg, blood, semen, vaginal fluid which can get into blood by, unprotected sex, cuts, sores, contaminated needles, can be transmitted from mother to chid during birth or breast-feeding
