Reproduction Flashcards
define asexual reproduction
~ is the process resulting in the production of genetically identical offspring from one parent, without the fusion of gametes
define sexual reproduction
~ is a process involving the fusion of 2 gametes to form a zygote. it produces genetically dissimilar offspring
what is & state function of sepal
- modified leaves which enclose & protect other parts of flower in bud stage
- encloses and protects the developing reproductive structures
functions of petals
in insect-pollinated flowers
- brighty coloured to attract insects for pollination
- provide a platform for insects to land
stamen
male part of the flower, consists of
- anther
- filament
function of anther
- produce pollen grains
- when anther matures, it splits open to release the pollen grains
- contains vascular bundle
what is & functions of carpels
consist of:
1. stigma - receives pollen grains, mature stigma secretes a sugary fluid that stimulates pollen grains to germinate
2. style - holds stigma in suiable position to trap pollen grains
3. ovary - will develop into a fruit after fertilisation, produces & protects 1 or more ovules
define pollination
~ is the trasnfer of pollen grains from the anther to the stigma
self-pollination vs cross-pollination
self-pollination is the transfer of pollen grains from anther to the stigma of the **same flower **or of a different flower on the same plant
cross-pollination is the transfer of pollen grains from one plant to the stigma of a flower in another plant of the same species
distinguish between self-pollinated flower & cross-pollinated flower
SP:
- flowers are bisexual w/ anthers & stigmas maturing at the same time
- stigma is situated** directly below** anthers
- in certain plants w/ bisexual flowers, some flowers never open. only self-pollination can occur in these flowers
CP:
- dioecious plants (eg, papaya bear either male of female flowers) cannot undergo self-pollination
- in many plants with bisexual flowers, anthers & stigmas may mature at different times
- stigmas of plants w/ bisexual flowers may be situated some distance away from anthers so that self-pollination is unlikely
compare insect-pollinated flowers with wind-pollinated flowers
Petals:
IP - usually large w/ brightly coloured petals to attract insects
WP - usually small & dull-coloured, w/o petals
Nectar:
IP - present, WP - absent
Scent:
IP - fragrants or sweet-smelling, WP - odourless
Stigmas:
IP - usually small, compact & do not protrude out of flower
WP - large, feathery, & usually protrude out of the flower to provide a larger SA to trap pollen
Stamens:
IP - not pendulous & usually do not protrude out of flower
WP - long pendulous filaments & protruding anthers so that pollen grains can be easily shaken out from the anthers
Pollen:
IP - fairly abundant, usually larger w/ rough surfaces so that they can readily cling onto the body of insects
WP - more abundant, have smooth surfaces & are **tiny & light **so that they are easil blown about by wind
Nectar guide:
IP - may be present on petal to guide insects towards the nectar
WP - absent
describe the growth of the pollen tube and its entry into the ovule followed by fertilisation
- After pollination, the pollen grains germinate after it comes into contact with the stigma, in response to the sugary fluid secreted by the mature stigma.
- A pollen tube grows out from each pollen grain. The male gamete enters the pollen tube.
- As the pollen tube grows, it secretes** enzymes to digest** the surrounding tissue of the stigma
and style. Thus, the pollen tube grows down the style into the ovary. - The pollen tube enters the ovule through the micropyle.
- Within the ovule, the tip of the two pollen tubes absorbs sap and bursts, releasing the two male gametes.
- The nucleus of one male gamete fuses with the nucleus of the ovum to form the zygote. This is fertilisation.
functions of: testes, scrotum, sperm ducts, prostate gland, urethra and penis
testis: each testis produces sperm & male sex hormones which are responsible for the development and maintenance of the secondary sexual characteristics in males
scrotum: outside the main body cavity and thus are at a slightly lower temperature than body temperature. The lower temperature is essential for the sperm to develop
properly
sperm ducts: after sperms are released from a testis, they travel through a sperm duct
prostate gland (+Cowper’s gland+seminal vesicle): secrete a fluid, containing nutrients & enzymes which nourish the sperms & stimulate them to swim activiely, which mixes with the sperms (mixture= semen)
urethra: both semen & urine pass out of the body through urethra
penis: an erectile organ which enters the vagina to deposit semen, containing sperms
functions of: ovaries, oviducts, uterus,
cervix and vagina
ovaries: produce eggs & hormones such as oestrogen and progesterone which are are responsible for the development and maintenance of the secondary sexual characteristics in females
oviducts: each ovary releases mature eggs into an oviduct - has a funnel-like opening lying close to the ovary which makes it easier for the egg to enter the oviduct, where egg is usually fertilised
uterus: where the fetus or unborn baby develops during pregnancy, has elastic muscular walls - the smooth
muscle tissue in the walls of the uterus contract to push the fetus out during birth, uterine lining - where the embryo implants
cervix: opening of the cervix allows menstrual blood to flow out into the vagina during menstruation
vagina: semen is deposited in the vagina during mating or sexual intercourse
briefly describe the menstrual cycle with reference to the natural variation in its length
- Menstruation is part of a cycle of events that takes place in the female reproductive organs every month. This cycle of events is called the menstrual cycle.
- The average menstrual cycle is 28 days.
- There is natural variation in the length of the menstrual cycles.
