IGCSE BIO 16. reproduction

germination

the process whereby seeds or spores sprout and begin to grow

conditions for seed germination

oxygen (for aerobic respiration) / water (to activate enzymes & chemical reactions) / suitable temperature (to activate enzymes)

scrotum

sac covering testes / hang outside the body, to keep testes cool, as sperm cannot withstand temperature above 37C

ovaries

produce ova / progesterone / oestrogen

puberty

the time at whcih sexual maturity is attained

asexual reproduction

a process resulting in the production of genetically identical offspring from one parent

sexual reproduction

a process involving fusion of nuclei of two gametes to form a zygote, and the production of offspring that are genetically different from each other

fertilisation

fusion of haploid nuclei of gametes to form a diploid zygote

advantages of asexual reproduction

only one parent needed --> so need to find mate / faster mass reproduction / less energy required, as no need to produce big flower or nectaries... / doesn't rely on pollinating agents / if parent well adapts to environment, offspring will also adapt well too

advantages of asexual reproduction, in crops

uniform genetically identical crop (with better yield, disease resistance...etc.) can only be produced

disadvantages of asexual reproduction

absence of genetic variation in offspring --> less ability to survive in different environment (disease resistance..etc.) --> less chance of evolution / overcrowding --> competition for resources

disadvantages of asexual reproduction, in crops

entire crop population can be destroyed by a disease, if they do not have genes of resistance

advantages of sexual reproduction

genetic variation in offspring --> more abilty to survive in different environment --> more possibility of evolution

disadvantages of sexual reproduction

need to find mate --> takes more time (slower) / more energy required, because of need to produce big, colourful flowers and nectaries... / rely on pollinating agents

disadvantages of sexual reproduction, in crops

uniform crop of genetically identical offspring is not possible

sepal

protect the flower, when it is a bud

petal

large and brightly coloured, to attract pollinators

anther

produces pollen grain, which contains male gamete

filament

supports the anther, holds it upright

stamen

another word to call male part of flower = anther + filament

stigma

site of receiving pollen grains

style

connects the stigma to the ovary

ovary

contains ovule, and forms fruit after fertilisation

ovule

contains female gamete (egg cell), and form seeds after fertilisation

carpel

another word to call female part of flower = stigma + style + ovary + ovules

pollination

transfer of pollen grain from anther of one flower to a stigma

!!POLLINATION IS ALWAYS SEXUAL REPRODUCTION!!

self-pollination

transfer of pollen grains from the anther of a flower to the stigma of the same flower or different flower on the same plant

cross-pollination

transfer of pollen grains from the anther of a flower from the anther of a flower to the stigma of flower on a different plant of same species

features of self-pollination

no or little genetic variation / lesser capacity to adapt to change in environment / no reliance on pollinators

features of cross-pollination

genetic variation / more capacity to adapt to change in environment / reliance on pollinators / energy need to be invested in bigger flowers and nectaries etc.

features of insect-pollinated flowers

large, conspicuous, colourful petals / scent & nectaries at the base / anthers & sticky stigma enclosed within petals /less, heavier, spiky pollen

features of wind-pollinated flowers

small, inconspicuous, green petals / no scent & nectaries / large anthers & feathery stigma dangling out of flower / smooth, light, more number of pollen

why self-pollination might be advantagous to a population of plants

prevents extinction / more chance of fertilisation & pollination / no need for pollinators / useful, if plants are isolated / for even smallest variation, pollination as sexual reproduction is better

fertilisation process

pollen grain lands onto the stigma --> pollen forms pollen tube (secretes enzymes to digest a pathway to the ovule through the style) --> male halpoid nuclei in pollen is delivered through pollen tube to the ovule --> fertilisation

types / roles of enzymes in germination

amylase & protease / break down stored food to release energy / diffuse into the embryo --> used for growth / needed in process of respiration

testes

produce sperm & male hormone (testosterone)

sperm ducts (vas deferens)

tube that transports semen from testes to urethra

prostate gland

secrete nutritious alkaline fluid (semen) in which sperm cells are transported / mucus

urethra

carries urine and sperm, but not at the same time : a ring of muscle around the urethra contracts, to prevent urine loss during sexual intercourse

penis

deliver sperm to the vagina for fertilisation / urethra runs down the center of penis

oviduct (fallopian tube)

ovum released from the ovary into the oviduct / site of fertilisation / cilia present, for propulsion of ovum

uterus

site of fetus development / develops spongy wall for embryo implantation, in case of pregnancy

cervix

narrow opening, which separates vagina from uterus

vagina

muscular tube opening outisde the body / receives male penis during the sexual intercouse / site of sperm deposition

adaptive features of sperm cells

acrosome : vesicle containing enzymes, which dissolves way through the jelly surrounding the egg cell / middle piece containing mitochondria to release energy for swimming / flagellum : allows swimming movements

adaptive features of ova

thick cytoplasm, containing lots of food stores / jelly coat : hardens after ferilization, to prevent entry of other sperms (NOT PROTECTIVE IN FUNCTION)

movement of spem cell / ova?

sperm cell : mobile / egg cell : motile (does not move by itself, move along by cilia and peristalsis)

food store in sperm cell / ova?

very little in sperm cells, as they respires the sugar in seminal fluid / ova has enough to last till implantation

number of sperm cells / ova produced?

sperm cells in millions constantly / ova one released per month

how ova is produced from ovary?

by meiosis

ovulation

release of mature ovum from ovary

embryo

ball of cells, which is the result of mitosis of zygote along the way through oviduct to uterus

another name of uterine lining

endometrium

placenta

disc-like structure formed from cells of embryo, soon after implantation

function of placenta

exchange of substances (oxygen, nutrients, excretory products.../ through diffusion / blood vessels close to each other)

placental barrier (prevents mixing of maternal and fetal blood, bursting of fetal vessels due to high pressure of maternal blood / prevents entry of pathogens from mother to fetus)

endocrine functions (secrete oestrogen & progesterone)

umbilical cord

connects endometrium to embryo / contains blood vessels from fetus

amniotic sac

a fluid-filled sac that cushions and protects a developing embryo and fetus in the uterus

amniotic fluid

fluid within the amniotic sac that surrounds and protects the fetus

functions of amniotic fluid

supports fetus / protects fetus against damage / provides constant temperature / allows movement of fetus / needs for bone & muscle & lung & gut development / needed for excretion / provides sterile environment

secondary sexual characteristics of male

enlargement of testes & penis / deepening of voice / broadening of shoulders / growth of hair in the pubir region, armpits, face, chest / rapid increase in growth rate

secondary sexual characteristics of female

increase in size and uterus & vagina / growth of breasts / widening of hips / growth of hair in the pubic region, armpits / rapid increase in growth rate

FSH (follicle stimulating hormone)

produced by pituitary gland / makes egg mature in the ovary / stimulates production of oestrogen from ovary

LH (luteinizing hormone)

produced by pituitary gland / causes ovulation

oestrogen

produced by ovaries / stimulates the thickening of uterus wall / inhibits the production of FSH / stimulates pituitary gland to make LH

progesterone

produced by ovary --> placenta / prevents menstruation (maintains the thick uterus lining) / increases the thickening of lining of uterus

corpus luteum

structure in ovary that forms from follicle left after ovulation / produces progesterone

day 0-5 of menstrual cycle

menstruation (shedding of uterus lining for last egg + unfertilized egg)

day 0-12 of menstrual cycle

new egg mature in ovary (FSH produced --> oestrogen produced from ovary --> FSH level drops)

day 12-16 of menstrual cycle

ovulation (release of one mature egg from one ovary) (LH (with FSH slightly) released and drop)

day 16-23 of menstrual cycle

egg travels through oviduct to uterus / fertilisation can happen

day 23 - 28 of menstrual cycle

if fertilized : implanted in uterus wall (progesterone & oestrogen level remains high)

if not fertilized : uterine lining starts to wear away (progesterone level drops due to dying of corpus luteum)

hormone graph of menstrual cycle

sexually transmitted infections (STIs)

infection that is transmitted via body fluids, through sexual contact

HIV (human immunodeficiency virus)

virus that makes the immune system so weak

AIDS (acquired immunodeficiency syndrome)

collection of diseases due to weak immune system by action of HIV

how HIV is transmitted

in blood (not insects) / in semen & unprotected sex / contaminated hypodermic needles / blood transfusion / at birth (when two blood vessels are closely in contact) / via breast milk / NOT SALIVA & BLOOD SUCKING INSECTS

prevention of HIV

use of condoms / antiviral drugs / reduction of shared needle usage by drug users