Transcript Asexual and sexual reproductionx

Plants
ASEXUAL AND SEXUAL REPRODUCTION
PLANTS REPRODUCE BOTH WAYS

Asexual reproduction: one living organism
involved.
 Offspring

identical to parent.
Sexual reproduction: requires one male and
one female parent.
 Offspring
different.
looks like parents but is genetically
DIFFERENT METHODS
Conifers and flowering plants: produce cones,
flowers and seeds.
 Algae, mosses and ferns: produce spores.

ASEXUAL REPRODUCTION
Does not involve meiosis or fertilization.
 One parent.
 Used by single-celled organisms such as
Archaea, bacteria, and protists.
 Plants use roots, stems or leaves to reproduce
asexually.

An advantage of asexual reproduction is that
an organism can reproduce by itself and it can
occur rapidly. Asexual reproduction can lead to
rapid population growth of a species.
 A disadvantage of asexual reproduction is that
only clones are reproduced – there is no
genetic variation. An organism would not be
able to adapt and evolve to a changing
environment.

THE TREMBLING ASPEN TREE

One forest = one individual
TYPES OF ASEXUAL REPRODUCTION

Binary fission: one cell divides to form two identical
cells. It duplicates its genetic material and then divides.
Each new cell has its own complete copy of the parent’s
genetic information.

Budding: part of the parent develops into a new
organism. The new organism then pinches off from the
parent and lives independently. The new organism is
genetically identical to its parent.

Fragmentation: the body of the parent breaks into two
distinct pieces, each can produce an offspring.
BINARY FISSION, BUDDING, FRAGMENTATION
SEXUAL REPRODUCTION


Increased genetic diversity of the offspring.
Characterized by two processes:





Meiosis
Fertilization: combination of two gametes (sex cells)
During meiosis, chromosomes usually cross over =
genetic recombination.
Primary method of reproduction for the vast majority
of visible organisms, including almost all animals and
plants.
Plants reproduce sexually: through flowers, cones or
seeds.
Sexual reproduction has the advantage of
providing lots of variation within a species,
helping it to survive when the environment
changes.
 The main disadvantage is that this process
takes a lot of energy and time. This means that
they can only produce small populations.

CHERRY BLOSSOM TREE
SEEDS

A seed contains all the requirements needed to
produce a new plant:
 The
embryo: small immature plant
 The cotyledon: food reserves
 The seed coat: protective cover
TWO TYPES OF SEEDS

Gymnosperm (conifer): “naked seed”
 The

seed only has the seed coat to protect it.
Angiosperm (flowering plant): “enclosed seed”
 The
seed has the seed coat as well as a second
cover (pod, shell or pulp).
 Pod
(beans)
 Shell (nuts)
 Pulp (fruits)
POD, SHELL AND PULP
SEXUAL REPRODUCTION


Reproduction in spore-producing plants:
 No production of seeds!
 Spores: cells that contain complete genetic material – can
become an immature plant without fertilization.
 Males spores become plants that produce spermatozoa and
female spores become plants that produce ovules. Then
comes fertilization.
Reproduction in conifers:
 Male cones contain male gametes
 Female cones contain female gametes


Seeds develop in female cones once the ovules are fertilized.
Reproduction in flowering plants:
 Pollination and Fertilization

Seed development

Seed dispersal
SPORES
CONES
FLOWERS (SEEDS)

Flowers can either have male reproductive
organs (stamens), female reproduction organs
(pistils or carpels) and often a flower has both.
Anther: where
pollen is
produced and
stored
Filament:
supports the
anther
Pollen: contain
male gametes
(spermatozoa)
Stigma: sticky
surface that
captures the
pollen.
Style: supports
the stigma
Ovary: contains
female gametes
(ovules)
Ovules: female
gametes
POLLINATION AND FERTILIZATION
Pollination leads to fertilization (zygote or fertilized
egg).
 Fertilization: male and female gametes combine.
 Pollen must land on the stigma in order to fertilize
the flower = pollination.

Self-pollination: pollen transferred to the pistil of the
same flower.
 Cross-pollination: pollen transferred to the pistil of a
different flower through wind or insects.

SEED DEVELOPMENT
1st stage of development: spermatozoon
(singular of spermatozoa) enters the ovule =
fertilization.
 2nd stage of development: Cell divides into
many cells that specialize themselves into
different structures for different functions.

SEED DISPERSAL
Seed dispersal: main mode or style of
dispersing seeds is through fruits.
 5 main agents of seed dispersal:

 Animals,
water, wind, the plant itself and humans
(sowing seeds).
LIFE CYCLE OF THE BEAN

Seed, seedling (young plant), adult plant,
flower, fruit and back to seed.