Chapter 14 - Asexual And Sexual Reproduction Flashcards
What is Asexual reproduction?
A process which results in the production of genetically identical offspring from one parent
What are some examples of asexual reproduction?
Binary fission in bacteria
Budding in yeast
Runners in plant
Potato tubers
How are potatoes formed from tubers?
The parent plant produces underground stems eventually forming tubers ( seed potatoes )
Sucrose is transported to the underground stems through the phloem in translocation
Sucrose is converted to starch and the stem swells to form a tuber
What is a haploid nucleus?
A nucleus containing only 1 set of chromosomes
What is a diploid nucleus?
A nucleus containing 2 complete sets of chromosomes
What is fertilisation?
The fusion of gamete nuclei
What does it mean when a flower is a hermaphrodite?
It means that flower contains both the male and female reproductive organs
What is the function of the sepal?
To protect the unopened flower
What is the function of the petals?
To attract insects in insect-pollinated flowers
What is the function of the anther?
To produce male gametes in pollen
What is the function of the stigma?
Collects pollen from pollinators or wind
What is the function of the ovary?
To produce the female gametes in ovules
What is pollination?
The transfer of pollen grains from an anther to a stigma
What is self-pollination?
The transfer of pollen grains from an anther to the stigma on the same flower or another flower on the same plant
What is cross-pollination?
The transfer of pollen grains from an anther to the stigma of a flower on a different plant of the same species
What are the advantages and disadvantages of Self-pollination?
Advantages
More chance of fertilisation
No reliance on pollinators
Disadvantages
Less variation
Less able to adapt to environmental change
What are advantages and disadvantages of Cross-pollination?
Advantages
Increase variation
More able to adapt to environmental change
Disadvantages
Less chance of fertilisatiion
Reliance on pollinators
What is the structure of an insect-pollinated flower like?
Large and colorful petals
Anther and stigma are inside the flower
Stigma is sticky
There is a nectary present
What is the structure of a wind-pollinated flower like?
Small, inconspicuous, and green petals
Anther and stigma dangle outside the flower
Stigma is feathery
There is no nectary
What is structure of a pollen grain from an insect-pollinated flower like?
Large size
Spiky and sticky
Smaller quantity produced
What is the structure of a pollen grain from a wind-pollinated flower like?
Smaller size
Smooth and light
Larger quantity produced
Describe the process of fertilisation in a plant
Pollen grain germinated and grows a pollen tube
The pollen tube grows down the style by digesting the style using enzymes released from the pollen tube and reaches through the ovule through the micropyle
The tip of the pollen tube breaks open and the male nucleus enters the ovule
Fertilisation occurs when the male nucleus fuses with the female nucleus inside the ovule
A zygote is formed as a result of fertilisation
Describe the changes in the number of chromosomes after pollination
Pollen grains are formed in anthers
During their formation, the number of chromosomes in the nuclei is halved by meiosis ( reduction division )
This means the male nucleus in the pollen tube is described as a haploid nucleus
When the main nucleus fuses with the female nucleus, the chromosome number doubles to form a diploid nucleus this process is called fertilisation
The zygote then divides by mitosis to form an embryo
What do the ovule, integuments and ovary become after fertilisation?
Ovule becomes a seed
Integuments become a testa
Ovary becomes the fruit
What do the radical and plumule grow into during germination?
The radicle will grow into a root
The plumule will grow into a shoot
What is the function of the cotyledons?
To store nutrients
What is the function of the micropyle?
Entry of pollen tube during fertilisation
Enter of water and diffusion of gases during germination
The radicle emerges from the seed through the micropyle
What are the 3 environmental conditions needed for germination? Give a reason for each condition
Presence of water, to activate the enzymes
Presence of oxygen, to allow for the release of energy from aerobic respiration
Suitable temperature, to increase enzyme activity
For a seed kept in the dark, why does the dry mass of the seed decrease because of respiration?
As respiration uses glucose, glucose is used up during respiration in the seed, which decreases its dry biomass
For a seed kept in the light, why does the dry mass of the seed increase?
As the seed carries out photosynthesis, the dry biomass of glucose used up for respiration is less then the dry biomass produced in the seed by photosynthesis
What are the advantages of asexual reproduction to a species in the wild?
All the offspring produced are genetically identical
If the parent is well adapted, the offspring will be adapted to the surroundings
Only one parent is required
The process is fast
Less energy required as there are no gametes needed
What are the advantages of asexual reproduction for crop production?
Population increases rapidly
All the desired features of the parent plants are passed on to the offspring
What are the disadvantages of asexual reproduction to a species in the wild?
Little or no variation
Evolution (formation of anew species) takes place slowly
Less able to adapt to a change in the environment
All individuals may be killed by the same disease
Overcrowding causes high competition for resources
What are the disadvantages of asexual reproduction for crop production?
Can exploit the same environment quickly as all the plants have the same demand for nutrients so they will exhaust the nutriet supply in the soil
This can be prevented by adding fertiliser to the soil
What are the advantages of sexual reproduction to a species in the wild?
Increases genetic variation
Evolution (formation of a new species) takes place more quickly
It easily adapts to a change in the environment
Seed dispersal can reduce competition for resources and allow colonisation of new areas
Less liable to be wiped out by disease
What are the advantages of sexual reproduction for crop production?
Can produce new varieties of plants
What are the disadvantages of sexual reproduction to a species in the wild?
Two parents are needed
Fertilisation may not happen and many pollens or seeds may be wasted
The loss of lots of energy
The process is slow
What are the disadvantages of sexual reproduction for crop production?
Desired features may be lost by cross-breeding
Plants may not be as well adapted to the area where parent grows
What is eutrophication?
When too much fertiliser is used so it goes in the river and promotes algae growth.
When algae grows in the river, they use up all the oxygen to decompose dead plants
So the fish cannot breath, so they die and their body is decomposed by the bacteria.
