4/15/2013 1 Plant Reproduction BI 103 Plant-Animal A&P Turn in Homework #1 Bryophytes Lycophytes Green algae: Chlorophytes Gymnosperms Angiosperms Pterophytes Land plants Vascular tissue Seeds Angiosperm specific adaptations • Unlike other plants they have: – Flowers – Double fertilization – Fruit Why do plants have flowers? In other words, what are the advantages of flowering? Discuss this question in groups Angiosperms: the Flowering plants Why do plants have flowers? Enlists partnerships with insects and other animals Less inbreeding Higher probability the pollen will reach the right plant They don’t have to produce as much pollen Alternating Generations In more advanced plants, the sporophyte generation is dominant.
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4/15/2013
1
Plant Reproduction
BI 103 Plant-Animal A&P
Turn in Homework #1
Bryophytes
Lycophytes
Green algae:
Chlorophytes
Gymnosperms Angiosperms
Pterophytes
Land plants
Vascular tissue
Seeds
Angiosperm specific adaptations
• Unlike other plants they have:
– Flowers
– Double fertilization
– Fruit
Why do plants have flowers? In other words, what are the advantages of flowering?
Discuss this question in groups
Angiosperms: the Flowering plants
Why do plants have flowers?
Enlists partnerships with insects and other animals
Less inbreeding
Higher probability the pollen will reach the right plant
They don’t have to produce as much pollen
Alternating Generations In more advanced plants, the sporophyte generation is
dominant.
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Alternation of generations modified
• Pollen= Male gametophyte
Contains sperm
• Ovule= Female gametophyte
Contains egg
How is pollen an adaptation to land?
Allows fertilization to occur even in the absence of available water.
Moss fertilization
Pollen grains
water
Anthers with microspores Microspore to pollen
1. The microspores divides by mitosis to produce two cells Generative cell (1n)
Tube cell== vegetative nucleus (1n)
2. A two layered wall develops around the microspore to become the pollen
3. The generative cell undergoes division once more 3n total (3 nuclei) in pollen
Double fertilization 1. Two pollen nuclei enter ovule
2. One fuses with the egg to form the zygote
3. The other fuses with 2 central cell nuclei to become the endosperm (3n), food for the zygote
Fruit development
Becomes the fruit! Becomes the seed!
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Why do we see such diversity in the flowers we see?
Theory: Coevolution of plants and pollinators Different flowers have evolved to attract different pollinators- plants have specialized to a specific group of pollinators
Pollination syndrome
Floral characteristics which attract a specific group of pollinator Bees, hummingbirds, moths etc
Allows flowers to specialize
May include mechanisms to exclude other pollinators
Pollination syndrome
What are the advantages to specializing to one species or one group of pollinator?
What are the disadvantage or risks?
Most flowers are ‘generalists’ and do not specialize.
Bees
Blue
Symmetrical
Smells sweet
Pollen
rewards
Nectar
rewards
Pheromone
rewards
Bees UV Markings
Bees can see in UV!
Pollinators: Bees Blue
UV marking
Symmetrical
Smells sweet
Nectar guides ---Example: Catalpa speciaosa
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Pedicularis attollens, common name:“Baby Elephant’s head”
Bumble bee pollinated
Specialized
Bee specialization
Pedicularis attollens
Buzz pollination
Technique only used by bees to release pollen from anthers– they must hit the right musical note!