Plant Life Cycles CHAPTER 30 Animals vs. Plants Plant Reproduction Animal Reproduction Life cycle...
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Transcript of Plant Life Cycles CHAPTER 30 Animals vs. Plants Plant Reproduction Animal Reproduction Life cycle...
Animals vs. PlantsPlant Reproduction
Animal Reproduction
Life cycleAlternation of generations
No alternation of generations
Gametes Haploid gametes Haploid gametes
Spores Haploid spores No spores
Gametes made by
Haploid gametophyte, by mitosis
Diploid organism, by meiosis
Spores made by
Diploid sporophyte, by meiosis
No spores
Alternation of Generations
• Plants have a double life cycle with two distinct forms:– Sporophyte: diploid, produce haploid spores
by meiosis.– Gametophyte: haploid, produce gametes by
mitosis.
Non-flowering plants
• Mosses, ferns, and related plants have motile, swimming sperm.
• What kind of environmental conditions would be required for reproduction in these plants?
• What kinds of limits does external reproduction impose on these plants?
Life cycle of mosses
• Follow the link and write down in your notes 1 page on the life cycle of mosses
http://www.microview.org.uk/millennium/pages/moss_lifecycle.htm
http://www.sumanasinc.com/webcontent/animations/content/moss.html
Moss Life Cycle
Life cycle of ferns
• Ferns, unlike some other plants, do not flower in order to propagate. Instead, they reproduce sexually from spores.
• The life cycle of a fern is very different from the life cycle of many other plants.
• While many plants grow a mature adult form straight out of the seed, ferns have an intermediate stage, called a gametophyte, which then grows into a mature fern.
•
• There are two distinct stages in the life cycle of ferns. The first stage is that of the gametophyte.
• Spores are produced on the underside of mature plants. These will germinate and grow into small, heart-shaped plants called gametophytes.
• The gametophytes produce both sperm and egg cells, and will fertilize itself, or others. Once the fertilization occurs, the adult fern will begin growing.
• The second stage in the life cycle of a fern is the adult stage. The fertilized gametophytes begin to look like a mossy growth.
Conifers
• 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.
• What are some advantages and disadvantages to wind pollination?
Angiosperms (flowering plants)• Plants that protect their seeds within the body
of a fruit.
• Make up ¾’s of all plants, including:
– Trees, shrubs, herbs,
grasses, water plants…
Structure of a Flower1. Pistil
2. Stigma
3. Style
4. Ovary
5. Stamen
6. Filament
7. Anther
8. Petal
9. Sepal
10. Receptacle
11. Stem
Male Reproductive Structure
The stamen consists of two parts: Anther and Filament
The anther is where meiosis occurs to produce haploid pollen
The filament is a stalk that supports the anther
Female Reproductive StructureThe pistil consists of
the stigma, style and ovary
The sticky stigma receives the pollen from the anther
The pollen grows a tube down through the style
Meiosis occurs in the ovary to produce haploid ovules
Reproductive Structures
• Petals: colourful
structures that attract pollinators.
• Sepals: surround and protect the flower bud.
Pollination
Wind, insects or other animals transfer pollen from the anther of one flower to the stigma of another
Flowers vary depending on pollination mechanism
Pollination VectorsWind Pollination: Dull, scentless flowers with reduced petalsBees/Butterfly Pollination: Brightcolor, nectaries, scent. They sip nectar, get pollen on coats, transfer pollen from flower to flower
Bird Pollination: Nectaries, brightcolors, tube-like flowers
Moth Pollination: White petals, open at night
Fly Pollination:Rank odor, fleshcolored petals
• Pollen Grain • Anther Sac
Pollen grains contain two haploid cells produced through meiosis.
1- The Tube cell – will grow the pollen tube. 2- The Generative cell – will go through mitosis to create two sperm cells.
OvaryEach ovule within an ovary has a micropyle (an opening for the pollen tube). The ovules’ megasporangium undergo meiosis to produce four haploid cells (3 die leaving 1 megaspore)The megaspore undergoes mitosis 3 times to produce 8 haploid cells within the embryo sac.
Fertilization
After pollen lands on the stigma, a pollen tube grows down through the style to ovary
Generative cell creates the two sperm nuclei Double fertilization occurs:
one sperm fertilizes the egg one sperm the two polar nuclei together
Result of Double Fertilization
The sperm nucleus and egg nucleus join to form a 2n (diploid) embryo
The other sperm nucleus and the two polar nuclei join to form a 3n (triploid) endosperm. The endosperm is the food supply for the embryo.
First link
Seed and Fruit Development After fertilization,
the petals and sepals fall off flower
Ovary “ripens” into a fruit
The ovule develops into a seed
Seed Dispersal Mechanisms-Allow plants to colonize new areas and avoid
shade of parent plant
Wind Dispersal - Flight mechanisms, like parachutes, wings, etc. Ex. Dandelion, maples, birch
Animal Dispersal - Fleshy fruits which animals eat, drop undigested seeds in feces or burrs which stick to animals’ coats
Gravity Dispersal - Heavy nuts fall to ground and rollex. acorns
Water Dispersal - Plantsnear water create floating fruitsex. coconuts
Plant Hormones
• Plant hormones can be divided into two classes:– Growth promoters: Auxins, Gibberellins,
Cytokinins– Growth inhibitors: Ethylene gas, Abscisic acid
Growth promoters
• Hormones can promote plant growth in two ways:– Stimulating cell division in meristems to
produce new cells.– Stimulating elongation in cells.
Auxin roles
• Auxins carry out multiple roles having to do with plant growth including:– Tropisms– Apical dominance– Growth of adventitious roots– Fruit growth
Tropisms
• Tropisms are the growth of a plant toward or away from a stimulus, including:– Phototropism: in response to light– Gravitropism: in response to gravity– Thigmotropism: in response to touch
How it works
• Nastic movements are rapid, reversible movements in a plant.
• Electrical potentials across cell membranes, similar to those in our nerve cells, signal plant cells at the base of the Mimosa leaf to rapidly lose water. This causes the leaf to droop.
Movies• Sensitive Plant:
http://www.youtube.com/watch?v=BVU1YuDjwd8
• Venus Fly Trap: http://www.youtube.com/watch?v=ktIGVtKdgwo&feature=related
Other examples
• Sunflowers follow the sun during the day.
• Leaves of many plants turn to follow the sun.
Day/Night length
• Some plants flower in response to the length of periods of darkness.
• Spring-blooming flowers are long night (short day) plants, while summer-blooming flowers are short night (long day) plants.
• Some plants are day-neutral.
Plant Communication
• Plants communicate chemically.
• Injured plants send out chemical signals that may– signal other plants to prepare for an attack.– attract other insects that eat the insects that are
attacking the plant.