Sexual Reproduction - plants
Identify three advantages of sexual Identify two advantages and one
reproduction compared to asexual. disadvantage of asexual reproduction
compared to sexual.
Put these in the correct order.
An enzyme called DNA helicase causes the weak hydrogen bonds to break – the DNA unzips,
forming a replication fork
The DNA unwinds
Any errors in the nitrogen base sequence are detected and corrected by an enzyme called DNA
polymerase I in a process called DNA mismatch repair – the error is detected, cut out and
replaced with the correct nitrogen base sequence.
Complementary nitrogen bases in the nucleotides join with the nitrogen bases in the single
stranded DNA in the 5’ to 3’ direction and this is called complementary base pairing: A-T and C-G.
The enzyme involved is DNA polymerase III. This forms a complementary strand of DNA.
The single stranded DNA act as a template due to the exposed nitrogen bases.
The backbones of the two strands of DNA are joined together by DNA ligase.
Each DNA molecule now consists of one old and one new strand.
2023 HSC.
Sheep have 54 chromosomes, while goats have 60 chromosomes. The hybrid offspring of a sheep-goat
pairing is called a geep.
(a) (i) State the diploid number of the sheep.
(ii) State the haploid number of the goats.
(iii) How many chromosomes will the sperm of the sheep have?
(b) During fertilisation, an egg from the sheep is fertilised by a sperm from the goat. Which of the
following will be correct for the geep?
A. n = 29 chromosomes
B. n = 52 chromosomes
C. 2n = 57 chromosomes
D. 2n = 114 chromosomes
Identify three advantages of internal fertilisation Internal and external fertilisation
compared to external fertilisation. (A) Are both examples of sexual reproduction
(B) Differ in that the former is an example of
sexual reproduction and the latter is an example of
asexual reproduction
(C) Differ in that in the former the sperm fuses
with the ova, but not in the latter
(D) Differ in that the former only occurs on land
and the latter only occurs in water.
Flowering Plants (Angiosperms)
Flowering plants reproduce using flowers.
Identify the parts of the flower.
Letter Name of Male/ How structure determines function.
flower part Female or
neither
A
Some flowers have both male and female parts, others have male or female parts.
The anther produces the pollen
(male gamete) which is haploid.
The pollen is transferred to the
stigma by an animal, the wind or
water during the process of
pollination.
The stigma has a sticky surface
sticky, which traps the pollen.
The pollen then germinates to
form a pollen tube which grows
through the style towards the
ovary.
Fertilisation occurs in the ovary
where the ova (haploid) fuses
with the pollen, forming the
zygote (diploid), which is inside
the ovule. The ovules becomes
the seeds and the fruit forms
from the ovary.
The seeds are then dispersed (by
wind, water or animals) and then
germinate when the conditions
are right (moisture, appropriate
day length, warmth) to form a
new plant
Self pollination is not of benefit to the plant, as genetic variation decreases, so plants
have efficient mechanisms to ensure cross pollination like anthers mature before the
stigma of a flower or they have separate male and female flowers, thus preventing
self pollination.
The main body of the angiosperm is the sporophyte and the gametophyte is where
fertilisation occurs.
Add n and 2n to the angiosperm lifecyle diagram below.
Seeds from plants like Acacias only germinate after bushfires. Account for this
adaptation.
Flowers can be wind or animal pollinated.
Use the diagrams below to complete the table below.
Features of flowers Wind pollinated Animal pollinated
Petals
Perfume
Nectar
Anthers
Pollen
Lifecycles of other kinds of plants – Moss, Ferns and
Gymnosperms
Simplified Moss Lifecycle
mitosis
Gametophyte (n)
mitosis
Spores (n) ova (n) and sperm (n)
meiosis fertilisation
sporophyte (2n) zygote (2n)
mitosis
Simplified Fern Lifecycle
mitosis
Gametophyte (n)
mitosis
Spores (n) ova (n) and sperm (n)
meiosis fertilisation
sporophyte (2n) zygote (2n)
mitosis
Simplified Gymnosperm Lifecycle
mitosis
Gametophyte (n)
mitosis
Spores (n) ova (n) and pollen (n)
meiosis fertilisation
sporophyte (2n) zygote (2n)
mitosis
Lifecycle of Fungi – not a plant.
The body of multicellular fungi consist of branching thread-like hyphae. They are
consumers that are haploid. (N)
The fungi reproduces via a fruiting body which produces spores – sexually or
asexually. The sexual reproduction increases genetic variation in the population.
Describe the similarities and differences of reproduction in plants (as shown
above) and generalised fungi. (4)
Questions
1. Identify the following as true or false:
True or False
In multicellular organisms, sexual reproduction is based on the
fusion of male and female gametes
Fungi only reproduce asexually
Mosses are plants with the gametophyte being dominant (more
obvious)
Ferns are plant that produce spores asexually
Seed dispersal relies on animals to carry the pollen
Pollen is equivalent to sperm
Sexual reproduction increases genetic diversity, allowing evolution
by natural selection
Sexual reproduction is the only way to ensure continuity of species
2. Match the term to the correct definition or description:
Haploid, Diploid, Sporophyte, Meiosis, Mitosis, Gymnosperm, Angiosperm
Contains 2 sets of chromosomes (2n)
Type of plant where seeds are formed from flowers
Type of cell division that produces four daughter cells that
are not identical
Group of plants where seeds are formed in cones
Type of cell division that produces identical daughter cells
The stage in plant lifecycle that produces haploid cells by
meiosis
Containing a single copy of each kind of chromosome (n)
3. (a) Label the structure of the components of the flower shown below.
(b)Annotate your diagram to show the processes of pollination and germination.
E. Define adaptations and explain how flowers are adapted for animal
pollination.
Syllabus outcomes
● explain the mechanisms of reproduction that ensure the continuity of a species, by
analysing sexual and asexual methods of reproduction in a variety of organisms,
including but not limited to:
– plants: asexual and sexual reproduction
– fungi: budding, spores
Prac: moss and fern spore cases, pine cones, flower dissection
