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What were the first seed plants?
Gymnosperms
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Of the phyla of living seed plants, which are gymnosperms?
The first four
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What is the main difference between gymnosperms and angiosperms?
Gymnosperm seeds do not develop within a fruit and angiosperm seeds do develop within a fruit
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Where do angiosperms come from?
They evolved from gymnosperms
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What phylum of seed plants do angiosperms make up?
The fith phylum
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What are the most recently evolved of all plant phyla?
Angiosperms
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What has happened to the gametophytes of seed plants during the course of evolution?
They have become highly reduced
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What two kinds of gametophytes do plants produce?
- Microgametophyte
- Megagametophyte
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What is a microgametophyte?
A very tiny male gametophyte that produces sperm
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What is a megagametophyte?
A relatively large female gametophyte that produces eggs
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What are microspores and where are they found?
The spores that produce microgametophytes, found in pollen grains
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What are megaspores and where are they found?
Spores that produce the megagametophytes found within ovules that are in an ovary
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What does a pollen grain consist of and what does it contain?
A few haploid cells surrounded by a thick protective wall, contains a microgametophyte that developed from a microspore
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When does a ovule become a seed?
When the egg inside of an ovule is fertilized
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How are pollen grains transported to female reproductive structure?
By wind, insects or other animals
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What is pollination?
The transportatino of pollen grains form a plant's male reporductive structures to a female reproductive structure of a plant of the same species
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What two things happen when a pollen grain reaches a female reproductive structure?
It attaches to the stigma and cracks open
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What happens after a pollen grain cracks open?
A pollen tube is formed from the pollen grain to an ovule enabling a sperm to pass directly to an egg
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What are most living gymnosperms?
Conifers
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What do conifers include?
Cedar, cypress, fir, hemlock, pine, redwood, spruce and yew
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What are the tallest living vascular plants?
Giant Sequoia
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What are the oldest species of vascular plants?
Bristlecone Pine
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What do most conifers have and how are they an adaptation?
Needle-like leaves used for limiting water loss
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Where are most conifers found growing?
In seasonally dry regions of the world
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What are many species of conifers very important sources of?
Timber and pulp
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What two kinds of cones to conifers form?
seed cones and pollen cones
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Where do see cones produce ovules?
On the surface of thier scales
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For seed cones, what happens during pollinization?
The scales of a seed cone are open, exposing the ovules
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Where do pollen cones produce pollen grains?
Produce pollen grains within sacs that develop on the surface of their scales
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What are the characteristics of pollen grains in conifers?
They are small and light, carried by wind to seed cones
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In pines and some other conifers, what does each pollen grain have?
A pair of air sacs that help to carry it in the wind
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Why do pollen cones produce huge quantities of pllen grains?
To insure that at least a few pollen grains will succeed in pollinating seed cones
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What often happens when pollen cones shed?
The pollen grains form a yellow layer on the surfaces of ponds, lake, pavement and car windshields
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What happens when a pollen grain lands near the ovule on a scale of a female cone?
A slender pollen tube grows out of the pollen grain and into the ovule
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Why does the embryo become dormant?
To wait until conditions are favorable
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What is the life cycle of a conifer characterized by?
A very large sporophyte (produces cones) alternating with tiny gametophytes (form on the scales of the cones)
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What is a seed?
A sporophyte plant embryo surrounded by a protective coat
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What is a seed coat?
The hard cover of a seed
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What is the seed coat formed from and what does it do?
The sporophyte tissue of teh parent plant and protects the embryo and other tissues in seed from drying out
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What three ways have seeds enabled plants to become better adapted to living on land?
- Dispersal
- Nourishment
- Dormancy
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How are seeds helpful through dispersal?
Enable offsrping of plants to be dispersed to new locations so the parent and offspring don't compete for water, nutrients, light and living space and helps plant species to migrate to new habitats so as not to go extinct
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How are seeds helpful through nourishment?
Embryo absorbs endosperm as nutrients before it grows roots
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How are seeds helpful through dormacy?
Can be dormant until conditions are favorable
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