Meiosis and Sexual Life Cycles (Ch. 13) -...
Transcript of Meiosis and Sexual Life Cycles (Ch. 13) -...
Vascular plants
• Phylum Pterophyta:
Ferns
Sperm flagellated
(swim)
Water required for fertilization
• Phylum Anthophyta
– Angiosperms
– Most advanced vascular plants
– Flowering
• Phylum Coniferophyta
Gymnosperms
Angiosperm plant reproduction
• Adult plant is a sporophyte
– Diploid
– Flowering
• Gametophyte
– Haploid
Flowers Organs
1. Sepal
2. Petal
Reproductive organs
3. Stamens - Filament
- Anther w/ pollen sacs (microsporangia)
4. Carpals (pistil) - Ovary
- Style + Stigma (sticky to receive pollen)
Stamen Anther
Filament
Stigma
Carpel
Style
Ovary
Receptacle
Sepal
Petal
(a) Structure of an idealized flower
Great diversity in flower types
• Flower types
– Complete flowers – have the 4 floral organs (both male and female)
elderberry
Each microspore contains:
1 generative cell produces 2 sperm cells
1 tube cell will produce pollen tube
(a) Development of a male gametophyte (in pollen grain)
Microsporangium (pollen sac)
Microsporocyte (2n)
4 microspores (n)
Each of 4 microspores (n)
Male gametophyte
Generative cell (n) forms 2 sperm
MEIOSIS
Ragweed pollen grain
Nucleus of tube cell (n)
MITOSIS
20 µm
75 µm
animation
Female Gametophyte = embryo sac
Location: Ovary
Megasporocytes(2n)
Produce 4 megaspores cells (1n) in ovules
1 megaspore survives
female gametophyte
Ovule
(b) Development of a female gametophyte (embryo sac)
Megasporangium (2n)
Megasporocyte (2n)
Integuments (2n)
Micropyle
MEIOSIS
Surviving megaspore (n)
3 antipodal cells (n)
2 polar nuclei (n)
1 egg (n)
2 synergids (n)
Fem
ale
gam
eto
ph
yte
(e
mb
ryo sa
c)
Ovule
Embryo sac
Integuments (2n)
MITOSIS
100 µ
m
Abiotic Pollination by Wind
Hazel staminate flowers (stamens only)
Hazel carpellate flower (carpels only)
Wind 20% of angiosperms
Inconspicuous flowers
Ex. grasses
No advantage to
colorful flowers
Pollination by Bees
Common dandelion under normal light
Common dandelion under ultraviolet light
Insects 65% of angiosperms
Nectar
Flowers bright colors
Bees most important
Double fertilization 2 sperm released to female gametophyte
- Attracted to egg by chemicals
- 1 sperm fertilizes egg to form zygote (2n)
- Other sperm unites with polar nuclei to form 3n endosperm
Anther
Pollen tube
Germinated pollen grain (n) (male gametophyte)
Ovary
Ovule
Embryo sac (n) (female gametophyte)
Egg (n)
Sperm (n)
Zygote
(2n)
Seed
Seed
Embryo (2n) (sporophyte)
Simple fruit
Germinating seed
Mature sporophyte
plant (2n)
(b) Simplified angiosperm life cycle
Key
Haploid (n)
Diploid (2n)
FERTILIZATION
True or false?
1. Plants are the only photosynthetic organisms on Earth
2. Plants are heterotrophic organisms
3. Plants reproduce by binary fission
4. Angiosperms use double fertilization in sexual reproduction
5. Fern plants do not produce pollen
6. All stems are above ground
7. Apical buds are also lateral buds
8. Xylem is a vascular tissue of plants
9. Dermal tissue may be covered by a cuticle
10. Adult sporophytes may contain embryonic , meristematic, tissue
11. The male gametophyte is a pollen grain
12. Soil bacteria fix atmospheric nitrogen
13. A complete flower has both anther and carpal
14. Microsporocyte cells are located in the plant ovary
15. Angiosperms contain the embryo in a seed
16. Haploid refers to a cell with 2 sets of chromosomes
17. Fertilization is the same process as pollination
Seed Development (Chapter 38)
• Each ovule develops into a seed
• Ovary becomes the fruit enclosing the seeds
• Seed coat - hard protection around embryo
• Seed is dehydrated
Tomato seeds with seed coat Apple seeds with seed coat
In the seed:
• Endosperm - Forms from 1 sperm + 2 polar nuclei
• (3n, triploid)
• Contains nutrients
3n
2n
Seeds with endosperm
Coconut has liquid and solid endosperm
The mature seed
• Dehydrated
• Dormant
– Metabolism/growth ceases
• Hard, protective seed coat
• Cotyledon
– Becomes first leaves (monocot and eudicot)
• Radicle
– Embryonic root
radish
Seed develops from ovule
Epicotyl
Hypocotyl
Cotyledons
Radicle
Seed coat
(a) Common garden bean, a eudicot with thick cotyledons
(a) Common garden bean
Seed coat Radicle
Hypocotyl
Cotyledon
Cotyledon
Hypocotyl
Epicotyl
Foliage leaves
Cotyledon Hypocotyl
Radicle, cotyledon, seed coat
Dicot
• Germination
– when conditions for growth are favorable
– Examples:
• Desert plant seeds germinate after substantial rainfall
• Some seeds require exposure to winter/cold
• Some must pass through animal digestive tract to soften seed coat
• Some require fire
Buttercup seed requires exposure to cold
Fruit forms from ovary
• Fruit protects seeds
• Aids in seed dispersal
• Dry fruits
– Nuts, legumes
Columbine
Milkweed
Sweet pea
Beans
Peanut
Runner Bean
buckwheat
sunflower
Wheat
Rice
Corn
Barley
Rye
Oats
Walnut
Hazelnut
Chestnut
Acorn
Fleshy fruits
Blackberry
Raspberry
Boysenberry
Loganberry
Cloudberry
Wineberry
Strawberry
Mulberry
Pineapple
Fig
Pomegranate
Date
Cornelian cherry
Goumi
Jujube
Jackfruit
Loquat
Kumquat
Persimmon
Kiwi
Guava
Longan
Lychee
Akee
Breadfruit
Camu Camu
Carambola
Chempedak
Custard apple
Durian
Guarana
Mamoncillo
Mango
Papaya
Pineapple
Rose apple
Tamarind
Pears
Apples
Quince
Chokeberry
Haw
Juneberry
Medlar
Rowan
Sorb apple
Cherry
Peach
Plum
Apricot
Olive
Lychee
Pin cherry
Coconut
Cucumber
Watermelon
Squash
Pumpkin
Honeydew melon
Sunberry
Lemon
Grapefruit
Limes
Citron
Mandarin
Clementine
Ugli fruit
Orange
Grapes
Tomatoes
Bananas
Avocados
Raspberry
Eggplants
Currants
Persimmons
Ovary
Stigma
Pea flower Ovule
Seed
Stamen
Pea fruit
(a) Simple fruit
Fruits classified by developmental features:
Simple Fruit
Develops from one ovary