Cambell Biology Ch. 30
360 Million Years Ago
When is the earliest evidence of seed plants' existence?
Miniaturization: Gametophytes are microscopic. This allowed for the evolution to seed plants. The spores over time were protected from UV radiation, being dried out, and other environmental stressors.
Pollen Grain: Can be carried by the wind and animals eliminating the dependency on water for sperm transport. This increased the sperms range. It most likely helped the colonization of dry habitats.
Multicellular Seeds: Spores are usually unicellular as seeds are multicellular. Which consists of an embryo protected by a layer of tissue, the seed coat.
Embryo Protection: The embryo in seeds is protected by the seed coat, which can allow the seed to live much longer than a spore. This allows the seed to be digested and pooped out farther away from its source.
What adaptations allowed seed plants to expand their range and deal with challenges of life on land?
Mosses and Other Non-Vascular Plants:
Gametophyte Dominant, Sporophyte Reduced
Ferns and Other Seedless Vascular Plants:
Gametophyte Reduced and Independant,
Seed Plants Gymnosperms and Angiosperms:
Gametophyte Reduced, Sporophyte Dominant
Describe how sporophyte and gametophyte stages differ (in terms of size and dominance)?
The arrangement of the spores can protect the gametophytes survive. They are protected from UV radiation, the elements, even from drying out.
What advantages exist from having a reduced gametophyte stage as in seed plants?
Whats the difference between Homosporous and Heterosporous?
This is what we needed in order for evolution of seed plants to take place. Without the male and female gametophyte production plants as we know them today, for the most part would not exist.
What is the significance of producing two kind of spores?
How are seed plant eggs fertilized?
Spore: Single cellular, is not a zygote. Not as protected. It is not fertilized. It needs to find another spore on it's own to become diploid.
Seed: Multicellular Zygote. (It is fertilized) Already diploid, and can grow where ever it lands. The embryo is protected by the seed coat.
What is the difference between spores and seeds?
Life Cycle of a Pine
Early gymnosperms lived in moist carboniferous ecosystems that were still dominated by lycophytes, horsetails, ferns, and other seedless vascular plants. 299 - 251 million years ago the climate became much drier. As a result the lycophytes horsetails and ferns that dominated the Carboniferous swamps were largely replaced by gymnosperms. Gymnosperms thrived in this dry environment, seeds and pollen flourished.
What ancient changes in climate led to the transition of a plant community dominated by gymnosperms?
Flagellated Sperm, 'maiden-hair' tree, fanlike leaves, tolerates pollution well.
Most are evergreens, retain their 'leaves' year round, Pines.
Flowers: Specialized for sexual reproduction. Pollen transfer via insects, birds and wind... The flower can have up to four floral organs; sepals, petals, stamens, and carpels.
Fruits: As the seeds develop from ovules after fertilization the ovary walls thicken and the ovary matures into a fruit.
Characteristics of Angiosperm
Produces microspores that develop into pollen grains containing male gametophytes. Contains the Filament and the Anther.
Stalk that holds the Anther.
A terminal sac that produces pollen. Held up by the Filament.
Make megaspores and their products, female gametophytes. It is the "container" where seeds are enclosed. Components are the Stigma, Style, and Ovary.
Sticky "tip" that receives pollen.
Leads from the stigma to the ovary. (stem-like)
Ovary is the housing for one or more ovules.
If fertilized will make a seed.
Usually green and encloses the flower before it opens, (like a rosebud).
Interior to the sepal, often brightly colored to attract pollinators. Wind pollinated angiosperms generally lack brightly colored parts.
Morphology of a Flower (angiosperm)
Flowers that have all four organs, Stamen, Carpel, Petal, Sepal .
Flowers that lack one or more organ.
Wind Adaptations: some seeds are in fruits, others are like propellers.
Water Adaptations: Coconuts
Animal Adaptations: Burrs that cling to fur or clothing. Seeds are eaten and then through pooping it out the seed is already packed in fertilizer and can be carried farther from its source.
Seed Dispersal Methods
Angiosperm Life Cycle
Insects help cross pollination, which enables plants to travel further, and become more spread out.
How have insects helped the spread of angiosperms throughout the world within the last 140 million years?
What are the differences between Monocots and Eudicots?
Seed plants are key sources of food, fuel, wood products, and medicine. Livestock are fed by seed plants. Plants die, we die.
What is the tie between our survival and plants?
Most gymnosperms are cone bearing plants like pines, firs, and redwoods.
The wall of fleshy fruits like grapes, plums, and tomatoes.
Divides and forms two sperm.
Produces a pollen tube
Female gametophyte that consists of only a few cells, one being the egg. This sac is from the ovule which develops in the ovary.
Transfer of pollen from one flower on one plant to the stigma of a flower on another plant of the same species. This allows for genetic variability.
a pore in the integuments of the ovule
One fertilization event produces a zygote and the other produces a triploid cell.
Seed leaves that develop on the sporophyte embryo.
The triploid central cell of the female gametophyte develops into a tissue rich in starch and other food reserves that nourish the developing embryo.