Name: ____________________________
Date: ___________________
IGCSE 0610 - Biology: Chapter B16 - Reproduction
Topic: B16.1 - Asexual reproduction; B16.2 - Sexual reproduction
Definition
Asexual reproduction is a process resulting in the production of genetically
identical offspring from one parent.
Sexual reproduction is a process involving the ____________ of the nuclei of
two gametes (sex cells) to form a zygote and the production of offspring that
are genetically different from each other.
Fertilisation is the fusion of gamete nuclei.
Examples of Asexual Reproduction [CORE]
Jade Plant (succulent)
Yeast Cells
Black Mold (Fungi)
Create Schools - S.Chew (Dec 2020)
Penicillium
1
Strawberry plants
Tulips & Daffodil
Cuttings
Create Schools - S.Chew (Dec 2020)
Potato Tubers
Rhizomes
2
Tissue Culture
Tissue Culture of Orchids
Asexual Reproduction in Animals - Hydra
Advantages and Disadvantages of Asexual Reproduction [Extended]
Advantages
Disadvantages
Relatively quick as no time wasted to
find a mate or wait for fertilisation.
Little genetic variation therefore
unlikely for adaptation to the
environment. (extinction of species)
Only one parent needed so no need
to spend energy to look for a mate.
Offspring may inherit bad traits from
the parent plant leading to less
resistance to pests and diseases.
(Monoculture of crops)
Energy saved can be put into rapid
growth or storage as starch.
No need for dispersal of seeds
(e.g. Potato tubers growing in the
same favourable environment as the
parent plant.)
Create Schools - S.Chew (Dec 2020)
Offsprings compete with parent plants
for nutrients, water and light.
(Lower crop yield)
3
B16.2 - Sexual Reproduction
Sexual reproduction involves the production of sex cells called gametes and they
are made in reproductive organs.
● The process of cell division that produces the gametes is called meiosis.
● In sexual reproduction, the male and female gametes come together and
fuse, that is, their cytoplasm and nuclei join together to form a single cell
called a zygote.
● The zygote then grows into a new individual.
In flowering plants the male gametes are found in pollen grains and the female
gametes, called egg cells, are present in ovules.
In animals, male gametes are sperm and female gametes are egg.
Chromosome Numbers [Extended]
In normal body cells (somatic cells) the chromosomes are present in the nucleus
in pairs.
● Humans, for example, have 46 chromosomes: 23 pairs.
● Maize (sweetcorn) has 10 pairs.
● This is known as the diploid number.
● When gametes are formed, the number of chromosomes in the nucleus of
each sex cell is halved. This is the haploid number.
Create Schools - S.Chew (Dec 2020)
4
● During fertilisation, when the nuclei of the sex cells fuse, a zygote is
formed. It gains the chromosomes from both gametes, so it is a diploid
cell.
Advantages and disadvantages of sexual reproduction
Advantages
Disadvantages
Gametes may come from the same plant or from different plants of the same
species which produce genetic
variation among the offspring.
Spontaneous changes in the gametes
when they are produced may result in
new combinations of characteristics.
Some combinations will produce
less successful individuals.
Successful combinations that have
greater survival value or produce
individuals which can thrive in new or
changing environments.
Plants that grow from seeds may
not have enough stored energy to
become an established plant without
support from the parent plant.
Plants that reproduce sexually may gain
resistance to diseases.
-
Scattering of seeds formed from sexual
reproduction can establish a new
population in new habitats.
Seeds that are scattered onto
barren land are wasted and will fail
to germinate.
Create Schools - S.Chew (Dec 2020)
5
B16.3 - Sexual Reproduction in Plants
Practical Skill
Identify and draw, using a hand lens if necessary, the sepals, petals, stamens,
filaments and anthers, carpels, style, stigma, ovary and ovules, of an insectpollinated flower.
Use a hand lens to identify and describe the anthers and stigmas of a windpollinated flower.
Create Schools - S.Chew (Dec 2020)
6
Wind Pollinated Flowers
Structure and Function of Parts of the Flower [CORE]
Structure
Function
Sepals
Petals
Anthers
Stigma
Ovaries
Create Schools - S.Chew (Dec 2020)
7
Definition
Pollination as the ____________ of pollen grains from the anther to the stigma
Pollen Grains from Insect Pollinated Flowers and Wind Pollinated Flowers
[CORE]
Feature
Insect Pollinated
Wind Pollinated
Surface
Size
Weight
Amount
produced
Fertilisation in Plants [CORE]
Fertilisation occurs when a pollen nucleus ___________
with a nucleus in an ovule.
Create Schools - S.Chew (Dec 2020)
8
Structural Adaptations of Wind- and Insect-pollinated Flowers [CORE]
Feature
Insect Pollinated
Wind Pollinated
Petals
Nectar
Stamen
Stigma
Pollen
Bracts
(modified
leaves)
Self Pollination and Cross Pollination [Extended]
Definition
Self-pollination is the transfer of pollen grains from the anther of a flower to
the stigma of the same flower, or a different flower on the __________ plant.
Cross-pollination is the transfer of pollen grains from the anther of a flower to
the stigma of a flower on a ______________ plant of the same species.
If a bee carries pollen from one of the younger flowers near the
middle of a lupin plant to an older flower near the bottom, this would
be self-pollination. If, however, the bee visited a separate lupin
plant and pollinated its flowers, this would be cross-pollination.
Advantages and Disadvantages of Self-Pollination and Cross-
Create Schools - S.Chew (Dec 2020)
9
Pollination
[Extended]
Advantages
Self-pollination
Cross-Pollination
Ensure survival even when
Definite genetic variation
there is a lack of pollinators
which gives a better chance
since pollen from the same
of adapting to changing
flower can fall on the stigma
conditions.
of the same flower.
Disadvantages Little genetic variation can
occur since the pollen and
Reliance on pollinators to
carry pollen to other plants.
stigma are genetically similar.
Fertilisation in Plants [Extended]
1. Pollen grain lands on _________.
2. Pollen ________ starts to grow out
of the pollen grain.
3. Pollen tube enters the __________
and then into the ______________.
4. The male nucleus from the pollen
grain travels down the pollen tube
and enters the _______________.
5. The male nucleus combines with the female nucleus to form a seed.
6. Each ovule in an ovary needs to be fertilised by a separate pollen grain.
Create Schools - S.Chew (Dec 2020)
10
Practical Skills [CORE/EXTENDED] (TB Pg 229 - 230)
Investigate and state the environmental conditions that affect germination of
seeds, limited to the requirement for water, oxygen and a suitable temperature
Write the steps to perform the following experiments and state the expected
results of the experiment and interpretation of the results.
Experiment 1: Investigate the need for water during germination
Create Schools - S.Chew (Dec 2020)
11
Experiment 2: The need for Oxygen
Create Schools - S.Chew (Dec 2020)
12
Lab Safety
Pyrogallic acid and sodium hydroxide is a caustic mixture. Use eye shields,
handle the liquids with care and report any spillage at once.
Experiment 3: Temperature and Germination
Create Schools - S.Chew (Dec 2020)
13
Create Schools - S.Chew (Dec 2020)
14
Important notes about control variables when planning experiments on
germination [CORE] (TB Pg 230)
Create Schools - S.Chew (Dec 2020)
15