24–1 reproduction with cones and flowers
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Slide 1 of 52
Biology
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24–1 Reproduction With Cones and Flowers
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24–1 Reproduction WithCones and Flowers
Alternation of Generations
Alternation of Generations
All plants have a life cycle in which a diploid sporophyte generation alternates with a haploid gametophyte generation.
Male and female gametes of a gametophyte plant join and form a zygote that begins the next sporophyte generation.
In some plants, the two stages of the life cycle are distinct, independent plants.
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24–1 Reproduction WithCones and Flowers
Alternation of Generations
In seed plants, gametophytes are found within tissues of the sporophyte plant.
In gymnosperms, they are found inside cones.
In angiosperms, they are found inside flowers.
Cones and flowers represent two different methods of reproduction.
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
Life Cycle of Gymnosperms
What are the reproductive structures of gymnosperms?
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
Reproduction in gymnosperms takes place in cones, which are produced by a mature sporophyte plant.
Gymnosperms produce two types of cones: pollen cones and seed cones.
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
Pollen Cones and Seed Cones
Pollen cones produce the male gametophytes, also called pollen grains.
Pollen grain (N)(male gametophytes)
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
Seed cones produce female gametophytes and are generally larger than pollen cones.
Female gametophytes develop in two ovules located near the base of each scale.
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
Within the ovules, meiosis produces haploid cells that grow and divide to produce female gametophytes.
Each gametophyte contains egg cells.
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
Pollination
The gymnosperm life cycle typically takes two years to complete.
The cycle begins as male cones release pollen grains.
Pollen grains are carried by the wind and reach female cones.
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
Meiosis
Fertilization
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
Male Cones
Mature sporophyte
Pollen cone
Pollen grain (N) (male gametophytes)
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
Female Cones
Mature sporophyte
Seed cone
Cone scale
Ovules
Diploid cell (2N)
Ovule
Four haploid cells (N)
Female gametophyte (N)
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
If pollen grains land on and enter an ovule, pollination occurs.
A pollen tube grows out of each pollen grain and releases sperm near an egg.
Egg cells
Discharged sperm nucleus
Pollen tube
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
Fertilization produces a diploid zygote which develops into a new sporophyte plant.
Zygote (2N)(new sporophyte)
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
This zygote grows into an embryo and is encased within what will develop into a seed.
Gametophyte tissue
Embryo (2N)
Seed coat(old sporophyte)
Seed
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24–1 Reproduction WithCones and Flowers
Life Cycle of Gymnosperms
The seed is then dispersed by wind.
When conditions are favorable, the seed germinates and its embryo grows into a seedling.
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
What are the reproductive structures of angiosperms?
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
Structure of Flowers
Flowers are reproductive organs that are composed of four kinds of specialized leaves: sepals, petals, stamens, and carpels.
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
Sepals enclose the bud before it opens and protect the flower while it is developing.
Sepal
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
Petals are often brightly colored and are found just inside the sepals.
Petals attract insects and other pollinators to the flower.
Petal
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
The male parts of a flower consist of an anther and a filament, which together make up the stamen.
Filament
AntherStamen
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
An anther is an oval sac where meiosis takes place, producing pollen grains.
Anther
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
The filament is a long, thin stalk that supports an anther.
Filament
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
The innermost floral parts are carpels, also called pistils, which produce the female gametophytes.
Carpel Style
Stigma
Ovary
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
Each carpel has a broad base forming an ovary.
The ovary contains one or more ovules where female gametophytes are produced.
Ovary
Ovule
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
The narrow stalk of the carpel is the style.
Style
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
At the top of the style is the stigma—a sticky portion where pollen grains frequently land.
Stigma
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
Ovary
Ovule
Carpel Style
Stigma
Ovary
Filament
AntherStamen
Parts of a Typical Flower
Sepal
Petal
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24–1 Reproduction WithCones and Flowers
Structure of Flowers
A typical flower produces both male and female gametophytes.
In some plants, male and female gametophytes are produced in separate flowers on the same individual.
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24–1 Reproduction WithCones and Flowers
Life Cycle of Angiosperms
Life Cycle of Angiosperms
Reproduction in angiosperms takes place within the flower. Following pollination and fertilization, the seeds develop inside protective structures.
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24–1 Reproduction WithCones and Flowers
Life Cycle of Angiosperms
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24–1 Reproduction WithCones and Flowers
Life Cycle of Angiosperms
Each flower contains anthers and an ovary.
Inside the anthers, each cell undergoes meiosis and produces haploid spore cells.
Each spore cell becomes a single pollen grain.
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24–1 Reproduction WithCones and Flowers
Life Cycle of Angiosperms
The pollen grain usually stops growing until it is released from the anther and deposited on a stigma.
Pollen grains (N)(male gametophyte)
Stigma
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24–1 Reproduction WithCones and Flowers
Life Cycle of Angiosperms
In the ovule, a single diploid cell undergoes meiosis to produce four haploid cells.
Haploid cell(N)
Ovule
Ovary (2N)
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24–1 Reproduction WithCones and Flowers
Life Cycle of Angiosperms
Only one of the four cells undergoes mitosis to produce eight nuclei.
The eight nuclei and the surrounding membrane are called the embryo sac.
Pollen tubeEgg cell
Sperm
Polar nuclei
Embryo sac (N)(female gametophyte)
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24–1 Reproduction WithCones and Flowers
Life Cycle of Angiosperms
The embryo sac is the female gametophyte.
One of the eight nuclei is the egg nucleus—the female gamete.
Pollen tube
Embryo sac (N)(female gametophyte)
Egg cell
Sperm
Polar nuclei
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24–1 Reproduction WithCones and Flowers
Life Cycle of Angiosperms
When fertilization takes place, this cell becomes the zygote that grows into a new sporophyte plant.
Endosperm(3N)
Zygote (2N)
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24–1 Reproduction WithCones and Flowers
Fertilization in Angiosperms
Fertilization in Angiosperms
If a pollen grain lands on the stigma of a flower of the same species, it grows a pollen tube.
Pollen grains (N)(male gametophyte)
Pollen tubes
Ovule
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24–1 Reproduction WithCones and Flowers
Fertilization in Angiosperms
The pollen tube grows into the style, reaches the ovary, and enters the ovule.
Pollen grains (N)(male gametophyte)
Pollen tubes
Ovule
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24–1 Reproduction WithCones and Flowers
Life Cycle of Angiosperms
One of the sperm nuclei fuses with the egg nucleus to produce a diploid zygote.
The zygote will grow into the new plant embryo.
Zygote (2N)
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24–1 Reproduction WithCones and Flowers
Fertilization in Angiosperms
The other sperm nucleus fuses with two polar nuclei in the embryo sac to form a triploid (3N) cell.
This cell will grow into a food-rich tissue known as endosperm, which nourishes the seedling as it grows.
Endosperm(3N)
Zygote (2N)
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24–1 Reproduction WithCones and Flowers
Fertilization in Angiosperms
Because two fertilization events take place between the male and female gametophytes, this process is known as double fertilization.
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24–1 Reproduction WithCones and Flowers
Pollination
How does pollination differ between angiosperms and gymnosperms?
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24–1 Reproduction WithCones and Flowers
Pollination
Pollination
Most gymnosperms and some angiosperms are wind pollinated, whereas most angiosperms are pollinated by animals.
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24–1 Reproduction WithCones and Flowers
Pollination
Wind pollination
•is less efficient than animal pollination
•relies on weather
Animal pollination
•plants have bright colors and sweet nectar to attract animals
•benefits both the plants and the animals that pollinate them
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Slide 47 of 52
24–1
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Slide 48 of 52
24–1
In a gymnosperm, fertilization occurs inside the
a. ovule.
b. pollen tube.
c. seed cone.
d. pollen cone.
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Slide 49 of 52
24–1
The pollen-producing structure of angiosperms is the
a. stigma.
b. carpel.
c. anther.
d. sepal.
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Slide 50 of 52
24–1
In an angiosperm, a structure that results from fertilization is the
a. female gametophyte.
b. pollen grain.
c. zygote.
d. ovary.
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Slide 51 of 52
24–1
Which term applies to the chromosome number of a seed plant embryo?
a. haploid
b. diploid
c. triploid
d. polyploid
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Slide 52 of 52
24–1
Pollination in most gymnosperms and some angiosperms is carried out by
a. water transport.
b. insects.
c. wind.
d. birds and bats.
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