PLANT REPRODUCTION

What Are the Basic Features of Plant Life Cycles?

How Is Reproduction in Seed Plants Adapted to Drier Environments?

What is the Function and Structure of the Flower?

Plant Reproduction

• Haploid: having a single set of chromosomes in each cell.

• Diploid: having two sets of chromosomes in each cell.

• Mitosis: cell division, which produces two genetically identical cells.

• Meiosis: reduction division, which produces four haploid reproductive cells.

Terms to Know

Plant Reproduction

Animal Reproduction

Life cycleAlternation of generations

No alternation of generations

GametesHaploid (n)

gametesHaploid gametes

SporesHaploid (n)

sporesNo spores

Gametes made by

Haploid gametophyte, by

mitosis

Diploid organism, by meiosis

Spores made by

Diploid sporophyte, by

meiosisNo spores

Plants and Animals

REPRODUCTION!

• Asexual Reproduction

• involves only 1 parent

• offspring genetically identical to parent

• involves regular body cells

• its quick

• Sexual Reproduction

• involves 2 parents

• offspring genetic mix of both parents

• involves specialized sex cells

• its slow

1:21

Asexual Reproduction

• Binary fission

• happens in bacteria, amoeba, some algae

• one parent cell splits into 2 identical daughter cells

• Budding

• happens in yeast, hydra, corals

• parent produces a bud

• bud gets detached and develops into offspring which is identical to parent

Binary Fission

Rod-Shaped Bacterium, hemorrhagic E. coli

2 daughter cells are identical to parent

Budding

Spore Formation

Fungi

FernFern

Vegetative Reproduction

Sexual Reproduction in Animals

• involves specialized sex cells called gametes

• the union of a male and female gamete results in the formation of a zygote that develops into a new individual

Sexual Reproduction in

Plants

(Pistil)

Male Parts

Female Parts

pollen (male) + ovule (female) → single-celled zygote → multi-

celled embryo (contained in a seed) → new individual

Sexual Reproduction in Plants

• stamen is the male part and contains pollen

• carpels or pistil is the female part and contains ovule (eggs)

• pollen grains from the anther are transferred to the stigma by the process of pollination

• self pollination (plant pollinates its own eggs)

• cross pollination (pollen from one plant pollinates another plants eggs)

Pollination

• flowers are designed to lure insects to help with the pollination process

• also wind, animals, birds can transport pollen

Sexual Reproduction Summary

Male Male GameteGamete

Female Female GameteGamete

Type of Type of UnionUnion

Result of Result of UnionUnion

Final Final ResultResult

PlantsPlants pollen ovule (egg)

pollination single cell zygote

multi-cell embryo

(in seed)

AnimalsAnimals sperm egg fertilization single cell zygote

multi-cell embryo

Some Organisms do Both

• most plants that produce seeds (sexual reproduction) can also reproduce asexually by things like cuttings or runners

• this gives them an advantage for survival

sponges and hydra mosses

Which is Better?It depends!

Asexual Reproduction

• advantages

• does not require special cells or a lot of energy

• can produce offspring quickly

• in a stable environment creates large, thriving population

• disadvantages

• limited ability to adapt

• face massive die-off if environment changes

Sexual Reproduction

• advantages

• lots of variation within a species

• able to live in a variety of environmental settings

• able to adapt to changes in the environment

• disadvantages

• needs time & energy

• produce small populations

• Natural “cloning.” Genetically Identical.

• Fast, no mate required.• Beneficial for plants that must

compete for scarce resources (Stable Environs).

• Part of a single plant divides by mitosis to give rise to a new plants.

• Spreading of runners (strawberries)• Production of bulbs (daffodils)• Sprouting of rhizomes (irises)

Asexual Reproduction

• Fusion of egg and sperm cells (haploid), from meiosis, gamete formation and fertilization.

• May be limited to a certain season.

• Slower than asexual reproduction.

• Allows genetic mixing, increasing variability in a population. Two parents give rise to genetically variable offspring. Favored in variable environments.

Sexual Reproduction

• All plant life cycles are characterized by alternating of portions (haploid-to-diploid-to-haploid).

• Multicellular diploid plants (sporophytes) and multicellular haploid plants (gametophytes) take turns producing each other during the reproductive life cycle.

• Sporophyte: diploid (2n), produce haploid spores by meiosis.

• Gametophyte: haploid (n), produce gametes by mitosis.

Alternate “Generations”

Life Cycle

• Diploid sporophyte (spore-forming plant) produces haploid spores by meiosis.

Life Cycle

• Spore germinates (begins to grow and develop); divides repeatedly by mitosis forming a haploid gametophyte (gamete-forming plant).• Gametophyte produces haploid sperm and

eggs by mitosis (gametes are produced at different times to prevent self-

fertilization).

• Sperm and egg fuse to form a diploid zygote (fertilized egg).

• Zygote undergoes repeated mitosis to form a new diploid sporophyte plant.

Life Cycle

• Mosses, ferns, and related plants have motile, swimming sperm.

• Reproduction in these plants requires wet conditions, and requires having male and female parts close together.

• Living conditions, plant size, and genetic mixing is limited.

Non-Flowering Plants

Moss and Fern Life Cycles

Group 1: Seedless, Nonvascular Plants

• Live in moist environments to reproduce

• Grow low to ground to retain moisture (nonvascular)

• Lack true leaves

• Common pioneer species during succession

• Gametophyte most common (dominant)

• Ex: Mosses, liverworts, hornworts

A. How Do Mosses/Liverworts Get Water?1. Nonvascular plant

2. Only about 2 to 5 cm tall, cling to damp soil, sheltered rocks, and the shady side of trees

3. Leaves have only one or two cells

4. Rhizoids: root-like fibers that are on the outside; take in water from surroundings Continue on to

next slide.

A. How Do Mosses/Liverworts Get Water?

5.Spores: cells that can develop into new organisms (seedless)

6.Close relative club mosses, horsetails, ferns, and spike mosses are VASCULAR

a.They grow thick and tallClick this link to see pictures of moss and

answer Question 1 on your sheet.

Life Cycle of Mosses1. Asexual reproduction: a

plant that needs only one type of cell to reproduce

a. This process uses spores

2. Sexual reproduction: a plant that needs two types of cells to reproduce

a. This process completes the cycle to allow reproduction

Continue on to next slide.

3. Alternation of generations: process of going from asexual reproduction to sexual reproduction

B. Life Cycle of Mosses

Click this link to learn more about what causes moss to grow and answer Question 2.

Moss Life Cycle

Haploid gametophytes

1)Moss gametophytes grow near the

ground (haploid stage)

2) Through water, sperm from the male

gametophyte will swim to the female

gametophyte to create a diploid

zygote

3) Diploid sporophyte will grow from zygote

4) Sporophyte will create and release

haploid spores

.....Diploid

sporophyte

eggegg

egg egg

malemale male malefemalefemalefemalefemale

zygotezyg

ote

zygote

zygote

5) Haploid spores land

and grow into new

gametophytes

.

groundHaploid gametophytes

6) The process repeats

Haploid gametophytes

.....sporophyte

eggegg

egg egg

malemale male malefemalefemalefemalefemale

zygotezyg

ote

zygote

zygote

Group 2: Seedless, Vascular Plants

• Vascular system allows

• Taller growth

• Nutrient transportation

• Live in moist environments

• swimming sperm

• Gametophyte stage

• Male gametophyte: makes sperm

• Female gametophyte: makes eggs

• Sperm swims to fertilize eggs

• Sporophyte stage

• Spores released into air

• Spores land and grow into gametophyte

• Ex: Ferns, Club mosses, Horsetails

Parts of a Fern1.Fronds: the

front leaves of ferns

2.Rhizome: underground stem which ferns grow from; roots sprout from this Continue on to

next slide.

Life Cycle of Ferns1. Reproduce by

alternation of generation; just like mosses

2. Fern seeds are on the fronds of the ferns and scatter on the ground

Click this link to see the different types of ferns and the life cycle of a

fern.

Fern Life Cycle

AdultSporophyte

.

...

1) Sporophyte creates and releases haploid spores

ground

.

.

.

.

ground

2) Haploid spores land in the soil

ground

3) From the haploid spores, gametophyte grows in the soil

Let’s zoom in

Fern gametophytes

are called a prothallus

4) Sperm swim through water from the male parts (antheridium) to the female parts (archegonia)…zygote created

Let’s zoom back out

eggegg

egg

zygote

zygote

zygote

ground

5) Diploid sporophyte grows from the zygote

sporophyte

Fern gametophytes

are called a prothallus

6) Fiddle head uncurls….fronds open up

ground

7) Cycle repeats -- Haploid spores created and released

.

.

..

fiddlehead

frond

.

.

.

.

ground

2) Haploid spores land in the soil

ground

3) From the haploid spores, gametophyte (called the prothallus) grows in the soil

Let’s zoom in

4) Sperm swim through water from the male antheridium to the female archegonia

Let’s zoom back out

eggegg

egg

zygote

zygote

zygote

ground

5) Diploid sporophyte grows from the zygote

sporophyte

fiddlehead

6) Fiddlehead uncurls….fronds open up.

ground

7) Cycle repeats

.

.

..

Review1) Why do moss grow so low to the ground?

2) Which stage is the main stage of moss: sporophyte or gametophyte?

3) How do moss reproduce?

4) What is the major difference between moss and ferns?

5) What are the leaves of ferns called?

6) What is needed for moss and ferns to reproduce?

7) Which stage is the main stage of ferns: sporophyte or gametophyte?

8) What stage is created when sperm and egg fuse: sporophyte or gametophyte?

9) Name the gametophytes of ferns.

• Conifers (also non-flowering plants) have reduced gametophytes.

• Male gametophyte is contained in a dry pollen grain.

• Female gametophyte is a few cells inside of the structures that become the seed.

Conifer Pollination

• Conifers are wind-pollinated plants.

• Chance allows some pollen to land on the scales of female cones.

• Pollen germinates, grows a pollen tube into the egg to allow sperm to fertilize the egg.

• Wind pollination is inefficient.

Conifer Pollination

• Showy flowers are the result of selection for more efficient pollination strategies.

• Flower parts are modified leaves. Those that were brightly colored attracted insects in search of pollen.

• Pollen itself is a protein-rich food for insects. Some plants offer other rewards, such as nectar.

Pollen In-between

• 43.2 How Is Reproduction in Seed Plants Adapted to Drier Environments?

• Seed plants (gymnosperms and angiosperms).

• Gametophytes develop within sporophytes.

• Reproduction can occur in dry habitats.

Seed Plant Reproduction

• Male gametophyte is surrounded by a protective coat called a pollen grain.

• The pollen grain encloses sperm cells in a watertight packet that can be easily transported to another plant.

• Egg-producing female gametophyte remains moist and protected within the sporophyte, and the pollen grain ensures that the sperm are delivered directly to the egg.

Seed Plant Reproduction

• The fertilized egg becomes enclosed in a drought-resistant seed.

• Consists of an embryonic plant and a food reserve encased within a protective outer coating.

• May lie dormant up to years waiting for conditions favorable for germination and growth.

Seed Plant Reproduction

• Non-flowering gymnosperms were the earliest seed plants.

• Gymnosperms bear male and female gametophytes on separate cones.

• Male cones release pollen grains that travel via wind to female cones.

Seed Plant Reproduction

Flowers

Sexual Reproduction - General

• Angiosperms produce flowers

• Flowers with both male and female reproductive organs are perfect flowers.

• Flowers that have only male or only female reproductive organs are imperfect flowers.

• Some angiosperms produce separate male and female flowers (imperfect flowers).

• Monoecious plants

• Dioecious plants

Angiosperms

• Sexual reproduction involves flowers and seeds.

• Flowering can be controlled by hormones, genes and/or environmental factors

Flower Parts

Flower Structure• Evolution of the flower – purpose is attraction of

pollinators.

• A change from radial to bilateral symmetry.

• Fusion or loss of whorls.

• Odors and colors.

• Nectar.

• Oddly shaped petals

• Flowers with 4 complete whorls = complete flower; flowers missing 1 or more whorls = incomplete flower.

Incomplete flowers

• Flowers are complete if they have all parts, and perfect if they have both male and female parts.

• Grass flowers: incomplete, usually imperfect (separate male and female flowers)

• A tulip is complete (though the sepals are the same color as the petals) and perfect.

Imperfect flowers

Angiosperm Life Cycle

Gametogenesis: Male

Gametogenesis: Female

Double Fertilization

Flower to Fruit

Ovule to Seed

Seed Germination