Of the phyla of living seed plants, which are gymnosperms?
The first four
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
Where do angiosperms come from?
They evolved from gymnosperms
What phylum of seed plants do angiosperms make up?
The fith phylum
What are the most recently evolved of all plant phyla?
What has happened to the gametophytes of seed plants during the course of evolution?
They have become highly reduced
What two kinds of gametophytes do plants produce?
What is a microgametophyte?
A very tiny male gametophyte that produces sperm
What is a megagametophyte?
A relatively large female gametophyte that produces eggs
What are microspores and where are they found?
The spores that produce microgametophytes, found in pollen grains
What are megaspores and where are they found?
Spores that produce the megagametophytes found within ovules that are in an ovary
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
When does a ovule become a seed?
When the egg inside of an ovule is fertilized
How are pollen grains transported to female reproductive structure?
By wind, insects or other animals
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
What two things happen when a pollen grain reaches a female reproductive structure?
It attaches to the stigma and cracks open
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
What are most living gymnosperms?
What do conifers include?
Cedar, cypress, fir, hemlock, pine, redwood, spruce and yew
What are the tallest living vascular plants?
What are the oldest species of vascular plants?
What do most conifers have and how are they an adaptation?
Needle-like leaves used for limiting water loss
Where are most conifers found growing?
In seasonally dry regions of the world
What are many species of conifers very important sources of?
Timber and pulp
What two kinds of cones to conifers form?
seed cones and pollen cones
Where do see cones produce ovules?
On the surface of thier scales
For seed cones, what happens during pollinization?
The scales of a seed cone are open, exposing the ovules
Where do pollen cones produce pollen grains?
Produce pollen grains within sacs that develop on the surface of their scales
What are the characteristics of pollen grains in conifers?
They are small and light, carried by wind to seed cones
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
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
What often happens when pollen cones shed?
The pollen grains form a yellow layer on the surfaces of ponds, lake, pavement and car windshields
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
Why does the embryo become dormant?
To wait until conditions are favorable
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)
What is a seed?
A sporophyte plant embryo surrounded by a protective coat
What is a seed coat?
The hard cover of a seed
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
What three ways have seeds enabled plants to become better adapted to living on land?
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
How are seeds helpful through nourishment?
Embryo absorbs endosperm as nutrients before it grows roots