UNIT 16 Reproduction Flashcards
asexual reproduction
a process
resulting in the production of genetically
identical offspring from one parent
MITOSIS used for asexual repr.
in asexual :
- no fusion of gametes so no mixing of genetic info
- produces CLONES
- no genetic variation in offspring
the advantages and disadvantages of
asexual reproduction:
a) to a population of a species in the wild
b) to crop production
adv:
- faster
- requires less energy
- Specifically in crop plants, asexual reproduction means that a plant that has good characteristics (high yield, disease-resistant, hardy) can be made to reproduce asexually and the ENTIRE CROP SHOWS SAME CHARACTERISTICS
disadv! of asexual
- offspring all genetically identical. reproduction does not produce genetic variation
examples
bacteria [asexual]
fungi [both]
small plants [both]
& animals [sexual]
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
in sexual rep.
gametes formed by MEIOSIS, a type of cell division which produces cells with half the chromosome number
zygote DIVIDES by MITOSIS
fertilisation
the fusion of the nuclei of
gametes, combining 23 chromosomes in sperm & 23 in egg resulting in a zygote with 46 chromosomes
nuclei of gametes are ____________ and that
the nucleus of a zygote is ____________
GAMETES HIPLOID GAMETES HIPLOID
ZYGOTE DIPLOID ZYGOTE DIPLOID
nuclei of gametes/GAMETES are HAPLOID and that
the nucleus of a zygote is DIPLOID
[haploid - contain only one set of chromosomes, in humans 23 chromos.
diploid - cell that contains two sets of chromosomes, one from each parent]
SEXUAL REPR. - adv:
adv:
- increases genetic variation
- species can adapt to new environments due to variation, giving them a survival advantage
- disease less likely to affect population due to variation
disadv:
- takes time and energy to find mates
- difficult for isolated members of the species to reproduce
pollination
- DEFINE
the transfer of pollen
grains from an anther to a stigma
the characteristics of an organism determined by both its environment and genes
asexual reproduction involves one parent and produces genetically identical offspring called clones
sexual reproduction involves two parents and the production of gametes which join together at fertilisation. This mixing of genetic info leads to variations in the offspring
Thee is far more genetic variety in sexual reproduction than in asexual, but sexual repr. is more risky because the organism must find a suitable mate
adv of genetic variation in wild
- genetic variation means that organisms can better survive changes to the environment
- some individuals may die but as the population is genetically diverse some will have the traits to survive
- prevents extinction
adv in crops
Having crop plants that are genetically different to one another is important for ensuring the crop can survive environmental change
stamen [anther, filament]
male reproductive organs of plant
carpel [stigma, style, ovary]
female reproductive organs of plant
filament [long, thin]
elevates anther exposing to wind and pollinators
anther
contains/produces and releases pollen (male gamete/sex cell)
male gamete is INSIDE the pollen grain
- hang outside the flower on long filaments so that wind can catch the pollen
ovary
- houses ovules; becomes fruit
produces ovules (female gamete)
sepal
thick protective leaves on outside of bud, peel back after flower blooms
protects unopened flower
receptacle
connects stem to flower
style [FEmale]
- long tube connecting stigma to ovary
elevates stigma, exposing to wind and pollinators
stigma [FEmale - top of the female part of the flower]
- sticky opening
catches pollen/collects pollen grains from wind and pollinators
- stigmas extend outside the flower and are often feathery to allow them to catch wind-borne pollen easily
petals
attract pollinators - birds, bees
colours attract them
brightly coloured in insect-pollinated flowers to attract insects
ovule
- develops female gametes; become seeds
contains female sex cells
found inside ovary
flowering plants reproduce …
sexually
cross pollination
the transfer of pollen from the anther to the stigma of a flower on another plant of the same species
- increases genetic variation
- increasing capacity to respond to changes in the environment, less reliance on pollinators
self pollination
the transfer of pollen from the anther to the stigma of the same flower or another flower on the same plant
Self-incompatibility - [NOT ON SYLLABUS]
proteins on the surface of pollen grains prevent them from germinating on genetically identical flowers
how to predict pollinator
through characteristics of a plant’s flower
e.g. of characteristics
- [just for understanding]
Flowers have:
- large, showy petals
- bright colours and distinctive patterns
- nectar guides
- attractive odours
Flowers can be:
- arranged in groups
- located apart from foliage
Colour: bee-pollinated
Flowers tend to be yellow, blue, purple or white because bees can see these colours.
Bees can also see ultra-violet pigments that may be present in flowers of any colour.
bee-pollinated
- Bright and attractive petals
- Often scented to attract pollinator
- anther;; Less anthers, usually held inside flower
- stigma;; Small and sticky – held inside flower
WIND-pollinated
small and plain
often green
no showy petals, odours or nectar. saves on energy and resources
Lots of pollen produced
in wind-pollinated,
& the stigmas are
anthers…
in general, plants grow…
flowers held…
stigmas are feathery and sticky and hang out of the flower in the air currents.
- Anthers dangle loosely on long filaments and can move freely in the wind.
- Plants grow together in large populations of the same species in an open environment which improves the chances of pollination.
- Flowers held above or below foliage to be more exposed to the wind.
Wind-borne pollen [ON SYLLABUS]
dry, not sticky ++ very small and light ;; adapted to be carried large distances.
smooth or dimpled for aerodynamic flight
Produced in large amounts
pollen adaptations - INSECT pollinated
Sticky/Patterned – adapted to stick to pollinator.
Small amounts produced.
Heavier.
Investigate and describe the environmental
conditions that affect germination of seeds,
limited to the requirement for: water, oxygen and a suitable temperature
Fertilisation occurs after… when…
occurs after pollination when a pollen nucleus fuses with an ovule nucleus
process -
Describe the growth of the pollen tube and its entry into the ovule followed by fertilisation
- pollen grows a pollen tube down the style
- the nucleus inside the pollen grain moves down the tube towards the ovule
- after fertilisation a zygote has been formed which will develop into a seed
ADDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD NOTES ABOUT SEXUAL REPRODUCTION IN PLANTS AND SEXUAL HORMONES
describe a STI as…
[used to be STDs, HIV human immunodeificiency virus causing AIDS acquired immunodeficiency syndrome]
an infection that is transmitted through sexual contact
what is HIV
human immunodeficiency virus (HIV)
is a pathogen that causes an STI
- HIV infection may lead to AIDS
methods of transmission of HIV
- use of non-sterile syringes and tools
- pregnancy. breastfeeding
- blood transfusion
- organ transplant
- UNPROTECTED sex
AIDS
- weakens immune system, leaves person at risk of death from other pathogens
how the spread of STIs is controlled
- use a condom during sex
- do not share needles for injecting drugs
- avoid breastfeeding if you are HIV-positive
- Get tested for STIs. Make sure you check if someone has an STI before sex. Make sure you trust them - some people may lie or try to pressure you.
female reproductive system
- production of gametes
- site of implanation
- site of fertilisation
- dilates during birth
- ovary T
- uterus X
- fallopian tube R
- cervix V
state meanings of
1. pollination
2. fertilisation
- transfer of pollen grains from the anther to the stigma
- gametes fuse
pollen nucleus fuses with a nucleus in an ovule
desc 2 implications of self-pollination
less variation ;
less chance for adaptation to new environment ;
more chance to pass on genetic disease ;
single plant can reproduce ;
well adapted to environment ;
more chance of fertilisation ;
whole crop would be susceptible to adverse factors like disease ;
Sexual hormones - difference between primary sexual characteristics & secondary
primary: present during development in the uterus and are the differences in reproductive organs etc between males and females
Secondary sexual characteristics = the changes that occur during puberty as children become adolescents; controlled by the release of hormones - oestrogen in girls and testosterone in boys
- both: growth of sexual organs and growth of body hair, emotional changes (i.e. more interest in sex and increased mood swings)
females
-breasts develop
-body hair grows
menstrual cycle begins
-hips get wider
males
-growth of penis & testes
-growth of facial & body hair
-muscles develop
-voice breaks
-testes start to produce sperm
menstrual cycle
- ~12 yrs, cycle takes 28 days. lasts around 5 - 7 days; signals beginning of cycle
- controlled by hormones
- during this cycle, uterus lining becomes THICKER in prep for an embryo potentially implanting
- no implantation in cycle = lining is shed/broken down during menstruation & cycle repeats
- after menstruation finishes, lining of the uterus starts to thicken again in preparation for possible implantation in the next cycle
ovulation - when does this occur (release of an egg)
occurs about halfway through the cycle (day 14) and the egg then travels down the oviduct to the uterus
menstruation is when in cycle
- menstruation is in the first 7 days of the cycle
FSH, follicle stimulating hormone (from pituitary gland)
- stimulates egg maturation in the follicles of the ovary, makes follicle mature
- stimulates follicles in the ovaries to secrete oestrogen
LH luteinising hormone
- at its peak, stimulates ovulation (release of egg into OVIDUCT)
- results in formation of a corpus luteum
oestrogen
- stimulates the uterus to develop a lining (to replace the lining lost during menstruation)
- post-ovulation, inhibits FSH and LH production in the pituitary gland
progesterone
- maintains & thickens lining of the uterus
- inhibits FSH and LH production
- if fertilisation doesn’t occur, levels drop & menstruation occurs
if fertilisation and implanation DOES occur…
- the corpus luteum will remain producing progesterone and keeping the uterus lining thick
- if fertilisation does NOT occur, the corpus luteum will break down, stopping the production of progesterone and causing menstruation
desb what happens at ovulation
- release of an egg into oviduct
name cell produced at fertilisation by fusion of 2 gametes
zygote
exam ques - ordering some events that occur in the menstrual cycle
secrete FSH ➡ follicles develop in ovary ➡ oestrogen from follicle cells ➡ repair&growth of uterine lining + stops FSH ➡ LH from pituitary gl. ➡ ovulation
H: FSH is secreted by pituitary gland
K: 1 or more follicles start to develop in an ovary
M: oestrogen is secreted by follicle cells
J: oestrogen stimulates repair & growth of the lining of the uterus
O: oestrogen inhibits secretion of FSH
N: LH is secreted by the pituitary gland
L: ovulation occurs
germination (seed sprouting)
requires THREE factors:
📌 water (needed to soften seed)
📌 suitable temperatures (makes sure it is the right time of year to sprout)
📌 oxygen (needed for respiration to produce energy for cell division)
desc what happens to structures to bring about fertilisation [3]
(stigma) is where pollen grain, germinates / develops
growth of pollen tube (down the style) ;
pollen tube / A, enters, ovule / B
OR;; (male) nucleus / gamete fuses with, female gamete /
nucleus / egg cell (nucleus) / C ;
forms zygote ;
diploid
3 adv of self-pollination for flowering plants
self-pollination perpetuates variety that is well adapted to habitat ;
greater chance of pollination
less wastage of pollen
3 disadv of self-pollination for flowering plants
less, variation ;
less chance of adapting to changing conditions / AW ;
more susceptible to diseases
dicots - mark scheme
network / AW, of veins / one (large) central vein ;
broad leaves ;
two, cotyledons / seed leaves ;
flower parts in multiples of, 4 / 5 ;
central / main, root ;
vascular bundles regularly arranged ;
