B15 - Reproduction (sexual & asexual) Flashcards
Define asexual reproduction & examples
-process resulting in the production of genetically identical offspring from 1 parent
eg. bacteria, fungi, plants (potato tubers, strawberry runners)
Advantages of asexual repoduction
-fast process
-can colonize new areas quickly
-needs only 1 individual
-genetically identical (favorable characteristics can pass on - artificial selection)
-if parents are well adapted to the environment, offspring will be too
Disadvantages of asexual reproduction
-little variation
-disease/ change in environment will kill all organisms; limited adaptability
-no dispersal; competition with parents
-negative traits are passed on
why is a population produced asexually unlikely to survive
-little genetic diversity
-offspring is only adapted to the environment of parent plant
define sexual reproduction & example
-process involving the fusion of the nuclei of 2 gametes to form a zygote & produce genetically different offspring
eg. humans, flowering plants
advantages of sexual reproduction
-genetic variation
-seed dispersal; no competition with parents
-can adapt to changes
-negative traits may not be passed on
-natural selection can occur
-can colonize new areas
disadvantages of sexual reproduction
-needs 2 parents
-slow process
-lots of seeds are wasted
-fertilization may not happen
-needs a pollinating agent
-good characteristics may not be passed on
-less energy efficient
define species
-group of organisms that can reproduce to produce fertile offspring
-only organisms of the same species can interbreed & produce fertile offspring
define diploid nucleus & example
-nucleus contains 2 sets of chromo.
eg. body cells
define haploid nucleus & example
-nucleus contains 1 set of chromo.
eg. gametes
define pollination
transfer of pollen grains from the anther to the stigma
define agent of pollination
method of transfer
2 main agents of pollination
-insect
-wind
features of an insect pollinated flower
-carpel
-stigma
-style
-ovary
-stamen
-anther
-filament
-ovule
-pollen grains
-nectary
-petals
-sepal
female part of an insect pollinated flower
-carpel:
-stigma
-style
-ovary
male part of an insect pollinated flower
-stamen:
-anther
-filament
functions of the carpel
-stigma - receiver pollen, sticky
-style - holds the stigma, pollen tube goes down it to the ovary
-ovary - produces ovules, site of fertilisation
functions of the stamen
-anther - produces pollen grains
-filament - supports the anther
functions of ovule
-contains female gametes, develops into the seed when fertilized
functions of the pollen grains
-contains male gametes
functions of nectary
-produces necter
function of nectar
-sugary fluid that attracts insects to feed
function of petals
-attracts insects for pollination; brightly coloured, scent, honey guidelines
function of sepal
protects the flower when in bud (before maturity)
adaptation differences between insect & wind pollinated flowers: petals
-insect pollinated: brightly coloured, large, scented, honey guidelines
-wind pollinated: small, inconspicuous, dull colours
-reason - wind doesn’t need to attract insects
adaptation differences between insect & wind pollinated flowers: anthers
-insect pollinated: upright, not flexible, inside the flower
-wind pollinated: hangs loosely/ dangles, outside the flower
-reason - wind can dislodge the pollen
adaptation differences between insect & wind pollinated flowers: pollen
-insect pollinated: large, spikey/ sticky, smaller quantities
-wind pollinated: light, smooth, small, larger quantities
-reason - more aerodynamic (increase air time), larger quantity increases the chances of pollination
adaptation differences between insect & wind pollinated flowers: stigma
-insect pollinated: small surface area, flat, sticky, inside the flower
-wind pollinated: long, feathery, hangs outside the flower
-reason - feathery stigma = larger surface area to trap pollen
adaptation differences between insect & wind pollinated flowers: nectaries
-insect pollinated: yes
-wind pollinated: no
-reason - no need to attract insects
define fertilisation in plants
-when a pollen nucleus fuses with ovule nucleus
seed & fruit formation
-zygote develops into an embryo & then a seed
-ovary wall increases in size, often becoming fleshy & develops into a fruit
define germination
process of a seed developing into a seedling
factors of germination
-water: activates enzymes & splits the seed coat
-oxygen: for aerobic respiration to release energy for growth from the stored sugar
-suitable temp: optimum temp for enzyme activity
how to control the factors of germination
-water - wet & dry cotton wool
-oxygen - layer of oil in cooled boiled water
-suitable temp - thermostatically controlled water bath
why add 20 seeds in the petri dish for experiment on germination
-to produce reliable results
define fertilization in humans
fusion of the nuclei from a male & female gamete
features of the male reproductive system
-seminal vesicles
-prostate glands
-sperm ducts
-urethra
-penis
-epididymis
-testes
-scrotum
note: for men, urine cannot mix with sperm so cannot pee while ejaculation
what is semen made of
sperm & seminal fluid
what does Seminal fluid contain & its use
-provides a medium for the sperm to swim in
-includes fructose sugar & alkaline salts to neutralize vaginal mucus
function of scrotum
-bag of skin that holds the testes outside the body to maintain optimum temp for sperm production
function of testes
-produces male sex hormones, testosterone
-produced male gametes, sperm
function of epididymis
-stores sperm (3-4 days)
-where sperm mature (enables them to swim)
function of penis
-inserted into the vagina for intercourse when errect
function of sperm ducts
-carry sperm from testes to urethra
-by a wave of contractions during ejaculation
function of seminal vesicles
-produces seminal fluid
function of prostate gland
-produces seminal fluid
-joins the sperm during ejaculation
function of urethra
-carries semen out of the body during ejaculation
-carries urine from bladder
features of the female reproductive system
-oviduct
-uterus
-cervix
-vagina
-uterus lining
-ovary
function of ovary
-2 round structures attached to the abdominal wall
-produces female gametes
-produces oestrogen & progestrone
-releases 1 egg per 28 days
function of oviduct
-tube btw ovary & uterus
-site for fertilization
-transfers egg from ovary to uterus by peristalsis & cilia
function of uterus lining
-spongy tissue
-site of implantation
-repaired by oestrogen, thickens by progesterone
-sheds during menstruation
function of uterus
-muscular wall chamber
-when embryo develops
-muscles contract during labour to dilate cervix & pull the baby out
function of cervix
-ring of muscle between uterus & vagina
-dilates during labour
function of vagina
-muscular tube
-lined with cell that produce mucus
-received penis during intercourse
-semen is deposited at the top
Sperm features
-haploid nucleus; contains 1 set of chromosomes
-head
-acrosome
-mid piece
-flagellum
egg features
-haploid nucleus
-cytoplasm
-jellycoat
sperm:
-site of production
-numbers produced
-mobility
-size
-testes
-300 million per day
-swims using flagellum
-0.05mm
egg:
-site of production
-numbers produced
-mobility
-size
-ovary
-1 every 28 days
-does not move independent by can be moved by oviduct
-0.1mm
adaptations of sperm
-flagellum - helps the sperm swim toward ovum (egg)
-acrosome - contains digestive enzymes that digest the jelly coat of the egg
-lots of mitochondria - aerobic respiration to release energy to swim
adaptations of egg
-food energy stores - provides nutrients for the zygote to develop in the uterus
-jelly coat - changes after fertilization to prevent more than 1 sperm from entering to ensure offspring has the right amount of DNA
what causes secondary sexual characteristics to appear & when
-by sex hormones (testosterone & oestrogen)
-during puberty
Male secondary sexual characteristics
-extra hair on face & body
-muscles to develop
-penis & testes enlarge
-sperm production
-deepening of voice
Female secondary sexual characteristics
-extra hair on underarms & pubic area
-hips widen
-development of breasts
-egg release & start of period
what does the menstrual cycle include
-ovarian cycle
-uterine cycle
-change in hormones
What does oestrogen & progesterone do
-oestrogen - repairs the uterus lining
-progesterone - thickens the uterus lining
-when both drops, mensuration is triggered
stages in the menstrual cycle
1) mensuration - uterus lining breaks down & passes through vagina (1-5 days)
2) in the ovary, an immature egg (oocyte) matures in a follicle. The follicle release oestrogen (6-13 days)
3) ovulation - egg is release from ovary (14 day)
4) corpus luteum releases progesterone after ovulation to prepare for pregnancy (15-21 days)
5) If not pregnant, oestrogen & progesterone levels will drop & trigger menstruation
6) if pregnant, oestrogen & progesterone are maintained to prevent mensuration
-lasts for 28 days
define Sexually Transmitted Infections (STI)
-an infection that is transmitted through sexual contact
eg. HIV, HPV, syphilis, chlamydia
define HIV
-Human Immunodeficiency virus
-pathogen that causes STI, may lead to AIDS
does all HIV positive people have AIDS
-Acquired Immuno-Deficiency syndrome
-no, untreated HIV targets your immune system which will become progressively weaker
Methods to prevent the spread of STI
-education/ awareness
-abstinence
-use a condom
-limit the number of sexual partners
-screen blood
-don’t re-use needles
-caesarian birth
-bottle feed baby
-get tested
-take medication to reduce risk
