ASEXUAL AND SEXUAL REPRODUCTION

Plants

PLANTS REPRODUCE BOTH WAYS Asexual reproduction: one living

organism involved. Offspring identical to parent.

Sexual reproduction: requires one male and one female parent. Offspring looks like parents but is

genetically different.

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.