Sexual Reproduction in Flowering Plants Flashcards
Reproduction has 2 basic functions, give them.
- replaces those organisms that die, maintaining the continuity of life.
- allows for an increase in numbers when conditions are suitable.
Name the 2 types of reproduction.
asexual, sexual
Whats asexual reproduction?
involves only one parent
What does mitosis not require and not involve?
doesnt require meiosis and does not involve sex cells (gametes)
What are sex cells called?
gametes
In asexual reproduction, comment on the appearance of offspring. Why is this?
offspring are genetically identical to the parent because all the cell divisions are by mitosis
Whats sexual reproduction?
involves the fusion of two sex cells or gametes (two parents)
What are gametes?
haploid cells capable of fusion
Whats essential for sexual reproduction? Why?
meiosis - to halve the chromosome number in the formation of gametes
In sexual reproduction, comment on the appearance of offspring. Why is this?
offspring show variation due to the mixing of genes from two parents
What happens gametes in sexual reproduction?
2 gametes fuse to form a diploid cell called a zygote
What is the receptacle and what does it do?
part of flower from which the flowering parts arise.
it supports these parts.
What colour are sepals usually?
What colour do they turn once the flower opens out?
green
brown
What are sepals and what do they do?
leaf-like structures that protect the flower then it is a bud
What are petals in animal-pollinanted plants and what do they do?
they are large and brightly coloured to attract animals
What are petals in wind-pollinanted plants like?
petals are small (or absent) and green
Are stamens male or female?
they are the male parts of the flower
Are carpels male or female?
they are the female parts of the flower
Stamens consist of?
filament and anther
Whats a filament? Contains? What does it do?
thin stalk,
contains vascular bundles,
bring food and water up to the anther and supports anther.
What 2 things does the anther do?
produces pollen grains,
releases pollen
Where does the anther produce pollen grains and as a result of what?
produces pollen grains on its inside as a result of meiosis
Each carpel has how many parts?
3
Name the carpel parts.
stigma, style, ovary
What does stigma do? Why is it suited to this job?
traps the pollen,
stigma is sticky to catch the pollen
Whats the style?
where the pollen tube grows
The style ‘tube’ goes from where to where?
stigma to ovary
Ovary contains what?
one or more ovules (and eggs)
Where are eggs found in the plant?
ovary
Whats the difference between a carpEl and a carpAl?
carpel = the female part of a flower
carpal = a bone in the wrist
What are the two male parts called?
anther, filament
What are the three female parts called?
stigma, style, ovary
Meiosis occurs in ovule to produce a structure called?
Embryo sac
After fertilisation the…
ovule becomes?
ovary becomes?
ovule = the seed
ovary = the fruit
Whats an adaptation of petals for wind pollination?
- small (or absent)
- green (or no colour)
- no scent
Whats an adaptation of petals for animal pollination?
- large
- brightly coloured
- scented
Whats an adaptation of pollen for wind pollination?
- large amounts
- light
- small
- dry
Whats an adaptation of pollen for animal pollination?
- small amounts
- heavy
- large
- sticky
Whats an adaptation of anthers for wind pollination?
- large
- feathery outside petals
- loosely attached to filament
Whats an adaptation of anthers for animal pollination?
- small
- inside petals
- firmly attached to filament
Whats an adaptation of stigmas for wind pollination?
- large
- feathery outside petals
Whats an adaptation of stigmas for animal pollination?
- small
- sticky inside petals
In relation to male gamete formation, cells lining the inside of the anther are?
diploid (2n)
In relation to male gamete formation, the anther consists of 4 chambers called?
pollen sacs
In relation to male gamete formation, each pollen sac is enclosed by?
an epidermis for protection and a fibrous layer
In relation to male gamete formation, the tapetum is what? What does it do?
an added layer of cells inside the fibrous layer which acts as a food store and supplies energy for cell divisions in the pollen sac
In relation to male gamete formation, inside each pollen sac are what called what?
diploid cells called microspore mother cells
In relation to male gamete formation, the microspore mother cells divide by what and form things called?
divide by meiosis, forming 4 haploid cells called a tetrad
Whats a tetrad?
4 haploid cells
In relation to male gamete formation, each tetrad breaks apart forming? What are they called?
4 separate haploid pollen grains called microspores
Whats the difference between exine and intine?
exine is thick outer wall
intine is thin inner coat
Each pollen grain/microspore has a thick outer wall ___ and thin inner coat ___.
exine
intine
In relation to male gamete formation, each pollen grain may go on and divide by? What does this form?
mitosis.
forming 2 haploid nuclei, the tube nucleus and generative nuclei
In relation to male gamete formation, after pollination the tube nucleus forms the?
pollen tube and degenerates
In relation to male gamete formation, after pollination the generative nucleus will undergo? Forming what?
mitosis, forming 2 male gametes
What happens the anther when the pollen grains have matured?
anther splits and peels back
Give account of the formation of embryo sac.
1) megaspore mother cell
2) is diploid
3) divides by meiosis
4) forms 4 haploid cells
5) 3 of these degenerate
6) divides by mitosis 3 times
7) embryo sac contains 8 nuclei
8) one becomes the egg
9) two form the polar nuclei
Definition of pollination?
is the transfer of pollen from the anther to the stigma
Definition of self-pollination?
involves the transfer of pollen from the anther to the stigma within the same plant
Definition of cross-pollination?
involves the transfer of pollen from the anther to the stigma between different plants
Discuss variation in self-pollination and cross-pollination.
self-pollination, no variation in offspring.
cross-pollination, show more variation (seeds)
Whats an example of a self-pollinated plant?
cereal
Name 3 methods of pollination.
wind
animals
water
Give a point on wind for pollination.
is very wasteful of pollen
Give examplse of wind-pollinated plants.
coniferous plants
grasses
oak
hazel
Give a point on animals for pollination.
more precise in carrying pollen directly to the stigma, less pollen wasted
The most common animal pollinators are?
insects
As well as insects, what else can carry pollen?
bats, birds
Give examples of insect-pollinated plants.
dandelions
daisies
buttercups
What stage comes after pollination?
fertilisation
Definition of fertilisation?
is the fusion of the male and female gametes to form a diploid zygote
Give 9 points on fertilisation.
(including double fertilisation)
1) pollen grain germinates
2) produces pollen tube
3) tube nucleus digests through the style
4) reaches the ovary
5) generative nucleus divides by mitosis
6) form 2 male nuclei
7) enter embryo sac
8) one male nucleus fuses with the egg nucleus to form a diploid zygote
9) the second male nucleus fuses with the two polar nuclei to form a triploid endosperm
Give 2 points on double fertilisation.
1) one male nucleus fuses with the egg nucleus to form a diploid zygote
2) the second male nucleus fuses with the two polar nuclei to form a triploid endosperm
The ovary develops what?
embryo sac
What are 2 advantages of cross-pollination?
prevents interbreeding
greater variation in the species
The fertilised ovule becomes?
the seed
A seed comes from?
the fertilised ovule
What does the radicle develop into?
a root
What does the plumule develop into?
the shoot
What’s a cotyledon?
a seed leaf
Whats a non-endospermic seed?
has no endosperm when fully formed
Whats an endospermic seed?
contains some endosperm when fully formed
The main foods stored by seeds are? What are these called
fats (or oils), proteins, starch = biomolecules
The walls of the ovule dry up and form?
the wall of the seed (testa)
Whats the walls of the ovule called?
integuments
During seed formation, the diploid zygote grows repeatedly by ___ and forms a group of cells that form the ___.
mitosis
embryo
(In seed formation) the embryo consists of?
the future root - radicle
the future shoot - plumule
In seed formation, some embryo cells grow to form?
cotyledons
During seed formation, the endosperm nucleus? What happens then?
divides repeatedly by mitosis producing many endosperm cells
these expand and absorb the nucleus and the endosperm acts as a food store
The endosperm acts as?
a food store
What foods are stored in seeds?
lipids and starch
2 examples of a non-endospermic seed?
broad bean, peanut
2 examples of endospermic seeds?
maize, corn
Whats the difference between monocot and dicot in terms of storing food?
monocot: rarely store food in cotyledons, instead the growing embryo absorbs food stored in the endosperm
dicot: food stored in the cotyledons
Instead of storing food what happens with monocots?
the growing embryo absorbs food stored in the endosperm
Give examples of monocotyledons.
grasses, daffodils
Give examples of dicotyledons.
broad beans, peanuts
Definition of a fruit?
a developed ovary
What becomes the fruit?
ovary
Two functions of fruit?
to aid seed dispersal
protect seeds
Name for the wall of the fruit?
pericarp
Why are grains also called fruits?
have an internal seed
Whats a false fruit? Give eg.
develop from other parts of a flower besides the ovary, eg. apple
The development of a fruit without a seed is called?
parthenocarpy
What are two ways seedless fruits can be formed? Give eg’s.
1) form genetically or by special breeding, eg: bananas, pineapples
2) spray plants with growth regulators, eg: auxins to form seedless grapes
Discuss ethene.
a plant growth regulator used to ripen fruit and is pumped into large storage containers, like for bananas
Definition of dispersal?
the transfer of a seed or fruit away from the parent plant
Dispersal is necessary to what? (4)
- avoid large numbers of seeds competing with each other
- increase the chance of survival for the plant
- find new areas for growth
- increase numbers of the species
Name the main methods of seed dispersal.
wind, water, animal, self
Give an example of wind dispersal and explain.
dandelions and thistles produce parachute devices that help disperse seeds widely.
sycamore produce fruit with wings which spiral down to the ground and increase the distance over which the seeds may be dispersed.
Give an example of water dispersal and explain.
coconut trees and water lillies have light air-filled fruits that float allowing them to be dispersed by rivers
Explain animal dispersal.
animals carry seeds or fruits long distances
Give an example of self dispersal and explain.
some fruits have mechanisms that catapult seeds away, pea pods that dry out and split open
Fruits dispersed by animals have either of two major adaptations, name them.
sticky fruits,
edible fleshy or succulent fruits
Describe sticky fruits. Give eg’s.
fruits with hooks may cling to an animal’s hair/fur and be carried away.
these seeds are dispersed by attaching to the external surface of the animal.
Eg’s: burdock, goose grass.
Describe edible, fleshy or succulent fruits. Give eg’s.
fruits attract animals by being brightly coloured with strong scents and lots of food.
the animal eats and digests the fruit but the seeds pass through the intestine unharmed.
these seeds are released with the faeces, which even acts as a fertiliser for them.
Eg: strawberries, blackberries, acorns, tomatoes.
Definition of dormancy?
period of low metabolic activity
/
period of no growth
Dormancy is brought about by what 4 ways?
- growth inhibitors which delay growth
- the testa may be impermeable to water or oxygen
- the testa may be too tough to allow the embryo to emerge
- may be a lack of suitable growth regulator needed
How is the knowledge of seed dormancy useful to humans?
- correct environment for storage
- optimum showing time
- maximise growing season
What are advantages of dormancy?
- survive adverse conditions
- gives time for dispersal (of the seed)
Definition of germination?
growth of a seed into a new plant
Name the three conditions needed for germination.
water, oxygen, temperature
How is water needed for germination?
needed to allow enzyme reactions to occur, the seed absorbs water from the soil causing the seed to swell and let enzymes function
How is oxygen needed for germination?
needed for aerobic respiration, its absorbed from the soil
How is temperature needed for germination?
must be suitable to allow enzyme reactions take place
What are the roles of water in germination?
- soften the testa
- activate enzymes
- increase metabolism
- transport nutrients
- dissolve nutrients
The role of digestion in germination?
provide soluble nutrients
The role of respiration in germination?
provides (or releases) energy for growth
State advantages of dispersal to the plant.
less competition with the parent plant,
colonise new habitats
Outline the events in germination.
1: seed absorbs water through a tiny hole called the micropyle and through the testa, water allowing enzymes be activated.
2: oils are digested to fatty acids and glycerol, starch is digested to glucose and proteins are digested to amino acids.
3: the products of digestion are moved to the growing embryo.
4: glucose & amino acids are used to make new structures like cell walls/enzymes.
5: the fats & some of the glucose are used in respiration to produce energy.
6: the dry mass of the seed falls due to the foods used in respiration.
7: as the mass of the food stores falls, the mass of the embryo increases as the food has been passed from seed to embryo.
8: the radicle bursts through the testa.
9: the plumule emerges above ground and leaves are produced.
10: once the first leaves start to photosynthesise, the dry weight of the seedling increases again.
Proteins being digested to amino acids refers to what human system?
digestive
The mass of the seed falls between days 0 and 9 due to?
respiration
From day 9 on, the mass of the seed increases due to?
photosynthesis
CHANGES IN DRY MASS DURING GERMINATION:
- why does the graph decrease?
- why does the graph increase?
decreases due to respiration and food being used up.
increases due to photosynthesis and food being made.
Name an example of germination in which the cotyledons remain below the soil.
broad bean
What does hypogeal mean?
cotyledons remain below the soil
What does epigeal mean?
cotyledons move above the soil
Discuss cotyledons remaining below soil.
- seed absorbs water, enzymes become active and radicle starts growing.
- radicle bursts out through testa and grows down due to geotropism.
- plumule emerges and region between cotlyedon and plumule called the epicotyl grows.
- cotyledons shrivel as food is transferred from them.
- radicle develops into the primary root.
- once above ground, plumule straightens and produces the first true leaves which become and green and start photosynthesising.
Discuss cotyledons moving above the soil.
- region between emerging radicle and cotyledons called the hypocotyl grows, causing the cotyledons to be carried above the soil.
- once above the soil, the fruit wall falls to the ground, the cotyledons open out becoming green and photosynthetic.
- plumule emerges from between the cotyledons and forms the first foliage leaves.
Name an example of germination in which the cotyledons move above the soil.
sunflower seeds
What is the pericarp?
fruit wall
What is the testa?
seed wall
The fruit wall is called what?
pericarp
The seed wall is called what?
testa
Benefits of dormancy for farmers?
optimum storage,
optimum ploughing/sewing time,
how to store seeds
when to sow seeds
As well as movement what does pseudopod do?
engulf prey
Function of anther, sepal and petal?
- produces pollen
- protects (developing flower
- attract pollinators
Two fertilisations occur after pollination, name the products of both fertilisations.
zygote - diploid
endosperm - triploid
