Chapter 14:reproduction in plants Flashcards
describe asexual reproduction
a process resulting in the production of genetically identical offspring from one parent
describe sexual reproduction
a process involving the fusion of the nuclei of two gametes to form a zygote and the production of offspring that genetically different from eachother
Example of asexual reproduction
1- bacteria
2- plants
3-an animal cell called hydra
how does bacteria reproduce asexually
Bacteria produces exact genetic copies of themselves in a type of asexual reproduction
how do plants reproduce asexually
They reproduce using bulbs and tubers,these are food storage organs which budding can occur producing new planets which generally are identical to the parent plant
how does “hydra” reproduce asexually
By growing buds which develop into young hydra before breaking away from the parent
Advantages of asexual reproduction for species in the wild
1-if an organism is well adapted to its environment,then all of its offspring’s will also be well adapted because they are genetically identical to their parents
2-Asexual reproduction requires only one parent, so when the organism is rare, it will be able to reproduce even if there is no possible partner nearby.
3-asexual reproduction can often be faster than sexual reproduction, producing more young in a shorter period of time
Advantages of asexual reproduction for crops
1- the grower can produce large number of genetically identical plants so that buyers know exactly what characteristics a plant will have
2-all plants will grow to the same height and ripen at the same time making harvesting and marketing easier
Disadvantages of asexual reproduction
1- limited genetic variation in population
2-population is vulnerable to changes in the conditions and may only be suited for one habitat
3-diseases are likely to affect the whole population as there is no genetic variation
define fertilisation
the fusion of the nuclei of two gametes
define gamete
a gemete is a sex cell which contains only one of each kind of chromosomes
Why does gamete have only half as many chromosomes as usual
so that when two of them fuse together,the zygote forms a correct number of chromosomes
how many chromosomes does a human body contain
46 chromosomes (23 pairs)
Give two examples of gametes
Egg cell and sperm cell
define diploid
having two complete sets of chromosomes (a zygote)
Define haploid
having only a single set of chromosomes ( a gamete)
define mitosis
Division of a cell nucleus resulting in two genetically identical nuclei
define meiosis
Division of a diploid nucleus, resulting in four genetically different haploid nuclei.
define a hermaphrodite
an organism which produces both make and female gametes
Advantages of sexual reproduction
1- increase genetic variation
2- the species can adapt to new environment due to variation,giving them a survival advantage
3- diseases less likely to affect population
Disadvantages of sexual reproduction
1-takes time and energy to find mates
2- difficult for isolated members of the species to reproduce
name the parts of a flower
The carpel ( stigma,style,ovary,ovule)
Receptacle
Flower stalk
Sepal
Nectary
Petal
Stamen (anther,filament)
Function of sepal
Leaf like structures that form a ring outside the petals of a flower
Function of petals
coloured structures that attract insects or birds to a flower
Function of stamens
The male parts of a flower
The function of filament
the ‘stalk’ part of a stamen
The function of anther
The structure at the top of a stamen inside which pollen grains are made
Function of pollen grains
Small structures which contains the male gametes of a flower
Function of carpel
The female part of a flower
Function of ovary
the part of the flower that holds the ovules
function of ovules
Small structures that contains the female gametes
Function of style
The part of a carpel that connects the stigma to the ovary
Function of stigma
The part of a flower that receives pollen
define pollination
the transfer of pollen grains from the male part of the plant to the female part of the plants
what is wind pollination
Wind pollination occurs when the pollen from once plant is transferred to the stigma of another plant of the same species
name 7 characteristics of insect polluted flower
1- large,conspicuous petals,often with guide lines
2- often strongly scented
3-often have nectaries at the base of petals
4-anther inside flower,where insect has to brush past them to reach nectar
5-stigma inside flower,where insect has to brush past it to reach nectar
6-sticky or spiky pollen grains,which stick to insects
7- large quantities of pollen are made because some will be eaten and some will be delivered to the wrong flower
name 7 characteristics of wind pollinated flower
1- small,inconspicuous petals,or no petals at all
2- no scent
3- no nectaries
4- another’s dang,e outside the flower,where they catch the wind
5- stigmas large and feathery and dang.s outside the flower,where pollen in the air may land on it
6- smooth,light pollen which can be blown in the wind
7-very large quantities of pollen made,because most will be blown away and lost
Define self pollination
The transfer of pollen grains from the anther of a flower to the stigma of the same flower,or a different flower or the same plant
Define cross pollination
The transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species
When does fertilisation occur
Fertilisation occurs when a pollen nucleus fuses with an ovum nucleus in the ovule
How does fertilisation occur
-If the pollen grain has landed on the right kind of stigma, it begins to grow a tube.
-the pollen tube grows down through the style and the ovary,towards the ovule.
-it’s secret enzymes that digest a pathway through the style.
-the pollen tube grows through the micropyle,into the ovule
-the pollen nucleus travels along the pollen tube and into the ovule and fuses with the ovule nucleus.
-fertilisation has taken place
Advantage of self pollination
-the plant does not have to reply on pollinators to transfer its pollen,pollen can simply fall from the anther onto the stigma
-if the plant is already well adapted to its environment,then it’s offspring are also likely to be well adapted
Advantages of cross pollination
-there is more genetic variation among the offspring,so there is a greater change of at least some of them being able to survive if there are changes in the environment
Define germination
Germination is the start of growth in the seed
Name the 3 factors required for successful germination
Water-it allows the seed to swell up and the enzymes in the embryo to start working so that growth can occur
Oxygen-so that energy can be released for germination
Warmth-germination improves as temperature rises as the reactions which take place are controlled by enzymes
Write down the method to investigate the conditions necessary for the germination of seeds
1- set up 4 boiling tubes each containing 10 cress seeds on cotton wool
2-leave tubes in set environment for a period of time:A,B and C incubated at 20 degrees and D placed in a fridge at 4 degrees
3-compare results and see which tube has the greatest number of germinated seeds
