Sexual Reproduction

1. Sexual
reproduction
Life cycles and the alternation
of generations

2. Sexual reproduction in animals
Animals have diploid body cells and haploid
gametes
The diploid body cells are made by mitosis
The haploid gametes are made by meiosis
At fertilization the haploid sperm and egg
fuse to produce the diploid zygote.
This then divides many times by mitosis to
grow into a new individual

4. Sexual reproduction in plants
In flowering plants
there are two
distinctive phases
of life cycle:
the diploid
sporophyte and
the haploid
gametophyte

5. Sexual reproduction in plants
The diploid
sporophyte
produces haploid
spores by meiosis.
The spores develop
into the haploid
gametophyte, which
then produces
haploid gametes by
mitosis

7. Sexual reproduction in plants
In plants such as
mosses and ferns,
the main plant is
the diploid
sporophyte.
It produces
(genetically
different) haploid
spores by meiosis

8. Sexual reproduction in plants
The spore grows
into the
gametophyte, which
produces
(genetically
identical) gametes
by mitosis.

9. Sexual reproduction in plants
In flowering plants
the water
dependent
gametophyte stage
in the life cycle is
much reduced.
The dominant stage
in the life cycle is
the sporophyte

10. Essential terms to know
Spore
A haploid cell that can be dispersed
It is the product of meiosis of a diploid cell

11. Essential terms to know
Gamete
A haploid cell, produced by mitosis of haploid cells.
It can fuse with another gamete to produce a diploid
zygote

12. Essential terms to know
Sporophyte
A multicellular plant that is diploid and
produces spores.

13. Essential terms to know
Gametophyte
A multicellular plant that is haploid and
produces gametes

14. Essential terms to know
NB These terms have been defined in terms
of plant kingdoms. A fungal spore is very
different!!!!

15. Essential terms to know
Alternation of generations
Terrestrial plants that have a life cycle with a
multicellular gametophyte and multicellular
sporophyte generation which alternates are
said to have a life cycle that shows
“alternation of generations”