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Lecture 19 : Gymnosperms, Angiosperms

Seed plants evolved from...
Spore-bearing plants
The seed is an important advancement why?
Extra layer of embryo protection
Easily dispersed
Seeds can be dormant and survive until environmental conditions are favorable
What does "gymnosperm" mean? Why?
"Naked seed"
Lack the flowers and fruits of angiosperms and the seeds are not enclosed by sporophyte tissue
Four major phyla of gymnosperms
Reproduction varies: which two have motile sperm and which have non-flagellated sperm?
Cycads and Ginkos have motile sperm, Conifers and Gnetophytes have non-flagellated sperm
What are all sperm carried within?
A pollen tube
Phylum Coniferophyta
Conifers; includes the tallest (coastal redwoods) and most massive (giant sequoia) trees
What is the oldest tree?
Bristlecone pine (~4800 years old)
Named Methuselah
Where are conifers usually found?
Drier and colder temperate regions (great forests in the Northern hemisphere)
Various species are useful to humans how?
Timber for construction
Taxol (used to treat cancer)
What has been the most important?
All seed plants are _____ and different spore types therefore give rise to...
Heterosporous; two different gametophytes
Male gametophytes (____ ____) develop from ______ found on male cones
Pollen grains; microspores

Pollen grains develop air sacs to assist in dispersal
Female pine cones
Larger than male, have woody scales
Phylum Cycadophyta- resemble ____ but are not flowering plants
What type of climate?
Tropical and subtropical
Similar life cycle to
Pylum Gnetophyta- only gymnosperms with...
Vessels in their xylem (as well as their tracheids)
Genera Ephedra is used to make ephedrine, which is a...
Drug that was used to treat respiratory problems (was pulled from the market because it caused heart attacks/ strokes)
Phylum Gingkophyta- is unique because it is...
The last of its kind (only one remaining species)
No longer exists in the wild
It is dioecious, meaning
Male and female reproductive structures are produced on separate trees
Have flowers and fruits and sporophyte covered seeds
As compared to gymnosperms, angiosperms have/are...
Are heterosporous
Have non-motile sperm
Ovules that are enclosed within sporophyte tissue at the time of pollination
Modified leaf that encapsulates the seeds and develops into fruit
What are flowers?
Modified stems with modified leaves
Flower bud that grows at the end of the stalk
Flower parts are attaches in circles called
Outermost whorl is the...
Next whorl consists of...
Sepals (most flowers have 3-5, they are usually green)
Next whorl consists of petals (usually colored to attract pollinators)
Third whorl contains _____, which produce...
Stamens; male gametophytes (pollen)

Each stamen consists of...
An anther (holds pollen) and a filament (stalk)
At the center of the fourth whorl is the...
Gynoecium, which houses the female gametophytes

Can have more than one carpel
Carpel has three major regions:
Ovary, stigma, style
Swollen base which consists of many ovules; ovary later develops into a fruit
Carpel tip, which is sticky or feathery so pollen can stick to it
Long neck or stalk that connects stigma to the ovary
Some plants don't have one
Some flowers secrete nectar from
Nectar contains sugars, amino acids, and other substances to attract pollinators
Angiosperm life cycle
Megaspore mother cell undergoes meiosis, followed by mitosis
Microspore mother cells also undergoes meiosis followed by mitosis (results in pollen grain, which is the male gametophyte)
The transfer of pollen from its source to a receptacle (stigma) of a flowering plant
Most pollination takes place between
Flowers of different plants
Pollination by what mechanisms?
Animals, wind, water, gravity
During pollination, the pollen tube enters the _____ ______ and discharges its contents (___ ___)
Embryo sac; two sperm
Both sperm are functional-
One unites with the egg and forms a zygote
The other sperm and the two polar nuclei unite forming a triploid endosperm nucleus
Endosperm tissue provides
Nutrients for the embryo of the flowering plant
Flower morphology and timing has often evolved with the
Pollinator, and vise versa (coevolution)
Among insect-pollinated angiosperms, what insect is the most popular?
Time of day that a flower is open may correlate with
When bees are active
Bird pollinated flowers are often what color?
Red (insects see in UV and aren't usually attracted to red)
Other insects that pollinate
Butterflies (flowers may have a perch)
Moths (pollinate at night, so flowers are scented and white)
Beetles and flies (flowers sometimes smell like rotting flesh)
Bats and small mammals
Some flowers (oaks, birches, cottonwoods, grasses) use _____ pollination
Wind; small, odorless flowers are grouped in large numbers and often hang down to better catch wind
Vehicle for dispersing the embryo to distant sites
The outer layer (integument) develops into
An impermeable seed coat (encloses the dormant embryo and stored food)
Seeds are important in four ways
1. Seeds maintain dormancy in unfavorable conditions
2. Seeds afford maximum protection when the plant is the most vulnerable
3. Seeds contain food to permit young plants to grow before photosynthesis begins
4. Seeds are adapted for dispersal (allows invasion of new habitats)
Other adaptations ensure that seeds will only germinate under proper conditions
-Some seeds only germinate when inhibitory chemicals leak out into the environment (requires water)
Some seeds require cold period (stratification)
Cones may not open to let out seeds unless exposed to heat from a fire (fire clears out competition and releases nutrients into the soil)
Some seeds only germinate after being passed through the digestive tract of the animal (which ensures dispersal), why?
Digestive enzymes break down the seed coat
Feces provide a natural fertilizer
Fruits are mature ____; during seed formation, the _____ develops into a fruit
Ovaries (ovary)
Fruits with fleshy coverings that are shiny black, red, or blue are usually dispersed by
Fruits with hooks and spines disperse by
Attaching to animals
Acorns and nuts distributed by
Small animals that bury them
Germination begins when
The seed absorbs water and metabolism resumes
Seeds can absorb a lot of water and often the water pressure...
Breaks the seed coat
What defines germination?
The emergence of the first root (radicle)
Ungerminated seeds in the soil are the
Seed bank