B15 reproduction Flashcards
describe asexual reproduction
- a process resulting in the production of genetically identical offspring
- from one parent
advantages of asexual reproduction
only one parent needed
- save time and energy in finding mate
allow organisms to reproduce very quickly
- spread thru area quickly
desired characteristics retained
disadvantages of asexual reproduction
identical copies of parent
- same characteristics
- vulnerable to environmental changes (eg disease)
describe sexual reproduction
- a process involving the fusion of the nuclei of two gametes to form a zygote
- production of offspring that are genetically different from each other
nuclei of gametes vs nucleus of zygote
gametes: haploid
zygote: diploid
advantages of sexual reprodction
variation
- more resistance to environmental changes and disease
disadvantages of sexual reproduction
- time and energy in finding a mate
- much slower than asexual
how many chromosomes in diploid nucleus
46
describe what is meant by a species
- group of organisms that can reproduce
- to produce fertile offspring
function of sepals
- protect growing flower
- prevent it from drying out
function of petals
- attract insects, birds, mammals (pollinators)
- to carry out pollination
function of stamens
- produce male gametes (pollen)
- provide correct structures and conditions necessary for transfer of pollen
function of filaments
- hold anther in position
- where it is able to transfer its pollen to an insect, mammal, or bird (pollinators)
function of anthers
- produce pollen grains
- containing plant’s male gametes
function of carpels
- produce female gametes
- provide correct structures and conditions necessary for fertilisation
function of style
- support and present stigma
- in position where it can receive pollen from insect, bird, mammal (pollinator)
function of stigma
trap pollen from other flowers
function of ovary
- contain ovules (which contain female gametes)
- which will develop into seeds after fertilisation
function of ovules
- female gametes produced and contained within ovules
- upon fertilisation, ovules develop into seeds
describe what is meant by pollination
transfer of pollen grains from an anther to a stigma
when does fertilisation in a plant occur
when pollen nucleus fuses with nucleus in ovule
explain structural adaptations of insect-pollinated flowers
- large and brightly coloured petals to attract pollinators
- anther located inside flower to brush against pollinators
- stigma located inside flower to brush against pollinators
- produce nectar to attract insects
describe structural adaptations of wind-pollinated flowers
- small and usually dull in colour, do not need to attract pollinators
- anther loosely attached and dangle outside flower so pollen can be blown easily by wind
- stigma loosely attached and dangle outside flower so can catch wind-borne pollen from other plants (often appear feathery)
describe anthers of wind-pollinated flower
describe stigma of wind-pollinated flower
requirements for germination of seeds
- water
- oxygen
- suitable temperature
function of testes
organ in which sperm cells and testosterone are produced
function of scrotum
- sack of skin that contains testes
- help keep them at slightly lower temp than rest of body
function of sperm ducts
muscular tube that connects a testis to urethra
function of prostate gland
- secrete fluid that nourishes and protects sperm
- mixture of liquid and sperm is called semen
function of urethra
tube that allows passage of semen and urine through centre of penis
function of penis
- during sexual intercourse, inserted into vagina
- allow sperm to transfer into female reproductive system
function of ovaries
- produces egg cells
- produces hormones oestrogen and progesterone
function of oviducts
- tube connecting an ovary to uterus
- fertilisation usually occurs here
function of uterus
organ in which embryo develops
function of cervix
ring of muscle between vagina and uterus
function of vagina
- elastic muscular canal through which newborn passes during childbirth
- during sexual intercourse, male penis inserted into vagina
describe fertilisation in humans
fusion of nuclei from male gamete (sperm) and female gamete (egg cell)
adaptive features of sperm
- flagellum
- many mitochondria
- presence of enzymes in acrosome
how does the flagellum help the sperm
- can move
- propel cell from one place to another
how does having many mitochondria help sperm
- organelles release energy by aerobic respiration
- needed to keep flagellum moving
how does the presence of enzymes in the acrosome in sperm help it
digestive enzymes allow sperm cell to pass through jelly coating on surface of egg cell
adaptive features of egg cells
- energy stores
- jelly coat that changes at fertilisation
explain how energy stores help an egg cell
- cytoplasm contains energy stores
- allow egg to survive for several days
- nourish zygote if fertilisation occurs (until it can implant in wall of uterus)
explain how jelly coat helps an egg cell
- allow sperm to attach
- create barrier to other sperm cells once one has successfully penetrated it and entered egg cell
compare male and female gametes
- egg cells much larger than sperm (0.1mm vs 0.05mm)
- egg cells cannot move on their own, sperm can move around 1-3mm per hour
- female usually release one egg cell per month. male can release 40 million and 1.2 billion sperm in single ejaculation
role of testosterone
development and regulation of secondary sexual characteristics during puberty
- facial hair
- voice box becomes larger
- voice “breaks” and becomes deeper
- shoulders and chest widen, muscle mass increases
- more hair on limbs and torso, pubic hair growth
- penis and testes grow larger
role of oestrogee
development and regulation of secondary sexual characteristics during puberty
- breasts enlarge
- hips widen
- more hair on limbs and torso, pubic hair growth
describe the menstrual cycle
- egg cells develop in ovaries within follicles
- day 14: follicle releases egg cell around once every 28d (ovulation)
- follicle develops into structure called corpus luteum
- from day 4, lining of uterus thickens so egg cell can implant into lining if fertilised
- if not, lining broken down and discharged from body thru vagina during menstruation (period)
describe what is meant by a STI
- sexually transmitted infection
- infection that is transmitted thru sexual contact
what is HIV and its consequences
- human immunodeficiency virus
- pathogen that causes an STI
- may lead to AIDS
methods of transmission of HIV
how is the spread of STIs controlled
- avoid sexual contact
- use protection (barrier method contraception)
- limit number of sexual partners
- increase testing