9.62M

Category:

biology

Key biological principle

For today’s biology lesson, you need to be:
Ready to think
Ready to discuss
thoughts and ideas
Ready to complete
activities
This Photo by Unknown Author is licensed under CC BY
This Photo by Uknown Author is licensed under CC BY-SANC
ALWAYS have the tools you may need:
writing equipment i.e. pens, pencils, ruler etc; lined, plain and
graph paper and a calculator

3.

4.

Previous knowledge
to build on
• Meiosis
• Sexual reproduction in mammals
• Fertilisation
• Parts of a flower
• Sexual reproduction in plants

5.

Useful words
for this week
• gametes
• acrosome
• zona pellucida
• fertilisation
• acrosome reaction
• cortical reaction
• fusion
• pollen tube

6.

STARTER:
WordWall

7.

8.

Week 16 BIO UK Explore – Gametes & Fertilisation
Textbook Ref: page 110 – 112 & 118

9.

Learning Objectives
3.6 understand how mammalian gametes are specialised for their
functions (including the acrosome in sperm and the zona pellucida
in the egg cell)
3.7 know the process of fertilisation in mammals, including the
acrosome reaction, the cortical reaction and the fusion of nuclei
DYK: know the process of fertilisation in flowering plants, starting
with the growth of a pollen tube and ending with the fusion of nuclei

10.

Compare and contrast oogenesis
and spermatogenesis
• Similarities:
Both have multiplication, growth and
maturation phases.
• Both begin with a primordial germ cell.
• Both are haploid during the maturation
phase.
Differences:
• Spermatogenesis starts at puberty and
oogenesis starts in the foetus.
• Meiosis 1 and 2 only occur during
specific events with oogenesis.
• Primary oocytes give rise to one ovum,
while primary spermatocytes give rise to
four spermatozoa.
• Oogenesis produces polar bodies.

11.

Question

12.

Mark Scheme

13.

How many marks?
1 mark
4 marks
3 marks
The majority of answers clearly recognised that one difference in the products
of oogenesis and spermatogenesis is that oogenesis produces polar bodies.
Many answers did not go beyond this as they described the difference in the
processes and not the products made. Highly scoring answers sometimes
made use of the phrase/aide memoir "sperm are many, mini and motile",
sometimes with "eggs are few, fat and fixed".

14.

Consequences
Take it in turns to add a statement to the process of fertilization but you don’t get to see what
has been written before!

15.

Question

16.

Mark Scheme
This question was answered reasonably well. Most candidates gained two marks for stating
that the acrosome contained enzymes and that these enzymes were required for digesting the
zona pellucida. Some mentioned the lack of acrosome reaction, although there were a few that
were confused with the cortical reaction. Only more successful answers referred to sperm cells
fusing with the cell surface membrane of the egg cell.
Some referred to the relative number of sperm cells in the second photograph, stating that
fertilisation would be less likely if there were fewer sperm cells. This was not credited, as the
question asked why the sperm cells in photograph B would not be able to fertilise an egg.

17.

Fertilisation in Mammals
Storyboard
Create a storyboard in groups/breakout rooms detailing how fertilisation takes place in
mammals. Use pages 140-141 in your textbooks to help you. Your teacher will share your
work and you will peer assess within the lesson.
Success criteria:
Included detailed scientific
information of the following:
fertilisation, acrosome, zone
pellucida, fertilisation membrane,
polyspermy, and conception.
Diagrams of each stage in the
fertilisation process, which are
detailed and appropriate.
Work is neat and well-presented.

18.

Video
Pollination:
List as many reasons as possible why
pollinators are important.
What other methods of pollination exist that
do not involve animals?

19.

Draw a flow chart of the formation
of pollen grain

20.

Draw a flow chart of the formation
of pollen grains

21.

Draw a flow chart of the formation
of egg cells

22.

Draw a flow chart of the formation
of egg cells

23.

Question
Describe how the structure of a pollen
grain differs from that of a sperm cell. (2)

24.

Draw a flow chart of the fertilisation
process

25.

Draw a flow chart of the fertilisation
process

26.

Question
Explain the function of the pollen tube in
fertilization in flowering plants. (2)

27.

Question
(QWC) Describe the process of fertilization
that takes place in flowering plants. (4)

28.

Question

29.

Mark Scheme

30.

Question

31.

Mark Scheme
(i) The majority of students correctly identified a structural difference between a spermatid and a
mature spermatozoan with the lack of a flagellum/tail being the most common answer. The most
common incorrect answer was that spermatids were diploid.
(ii) Most students were able to identify that the spermatid was unable to fertilise the egg, most
commonly because they could not swim, although many described the importance of the
acrosome reaction well. Some students discussed competition and cooperation between sperm
which was not relevant to this question.
(iii) Marks were most commonly awarded for some idea of the "best" sperm fertilising the egg,
with few students going on to refer to the inheritance of advantageous alleles or natural
selection. A lot of students described the need for many sperm/acrosome reactions being
needed to penetrate the zona pellucida. The most common incorrect answers referred to many
sperm being needed for increased genetic variation.
(iv) The most common correct answer referred to the idea of selection and designer babies.
Many students made some not very clear reference to abnormality, with clearer responses
correctly identifying that a gene mutation (that caused the disorder) could be inherited because
of the technique. Common answers that were not given credit were the usual references to
religious or cultural arguments and others referred to the cost of treatment and stress to parents.

32.

Question
Sexual reproduction in plants includes the transfer
and fusion of gametes. The diagram below shows
part of a flower with two pollen grains and their
pollen tubes.
The diagram also shows an enlargement of one of
the pollen tubes and the pH of the cytoplasm in
each region of this tube.
(a) At stage 1, the pollen grain contains the haploid
generative nucleus. Explain what is meant by
the term haploid nucleus. (2)
(b) Describe the changes in the pH of the pollen
tube shown in the diagram. (2)

33.

Answer
Answer
• idea of half the number of chromosomes
found in a {normal body cell/somatic cell
/ eq} (1)
• idea of containing one chromosome from
each homologous pair (1)
• the type of nucleus found in {gametes /
sex cells / eq} (1)
• a nucleus is (an organelle / (double)
membrane-bound structure / eq) (1)
Answer
• idea that pH increases then decreases (1)
• correct manipulation of figures in an
appropriate context e.g. overall 0.2
change / eq (1)

34.

Key Biological Principle
Your teacher will put you into break out rooms to work through this activity in smaller groups.
You will then come back and share your thoughts.
Read page 125 and discuss the questions.

35.

Summary of Discussions

36.

Apply
Week 16 BIO UK Apply – Gametes & Fertilization

37.

A suggestion for the creation of a revision aid
Gametogenesis
phases
Diagrams
Pollen formation
Egg cell formation
Fertilisation
Sporophyte
generation
Gametophyte
generation
Gametogene
sis
Formation of pollen
Formation of egg
cells
Reproduction
in Plants
Comparison to
mammals
• Gametogenesis
• Fertilisation
Pollination
Fertilisatio
n
• Fertilisation
process
• Double fertilisation
• Biotic (e.g. insects)
• Abiotic (e.g. wind)