Chapter 30 - Plant Diversity II Flashcards
What are the advantages of producing a seed?
- seeds can move away from the mother plant; do not have to be attached
- seed plants are dominant producers on land
- 12000 years ago humans began cultivating plants
Name five derived traits of seed plants.
1) Reduced Gametophytes
2) Heterospory
3) Ovules
4) Pollen
5) Seeds
Reduced gametophyte
microscopic male and female gametophytes (n) are nourished and protected by the sporophyte (2n)
Heterospory and what types?
Other or different spores
microspore (gives rise to a male gametophyte) megaspore (gives rise to a female gametophyte)
Ovules
Inside each ovule, a female gametophyte develops from a megaspore and produces one or more eggs
Pollen
pollen grains make water unnecessary for fertilization; pollination occurs when pollen is transferred to the part of the seed plant that contains the ovules
Seeds
survive better than unprotected spores; can be transported long distances (by wind or animals)
Pollination Tip
- ovules not completely enclosed in sporophyte tissue at pollination
Where is the female and male gametophyte located in a seed plant?
-
What are the four groups of gymnosperms?
- Coniferophytes
- Cycadophytes
- Gnetophytes
- Ginkgophytes
- all lack flowers and true fruits
Conifers
- largest gymnosperm phylum
- tallest and oldest vascular plants
EX. pines, spruces, firs, cedars
Pine (conifer)
- cluster of two to five tough, needle like leaves
- Produces male and female cones
- microsporangia develop into four-celled pollen grains
- megasporangium produces megaspores one of which becomes female gametophyte
Cycadophytes
- resemble palms, but are not flowering plants
- heights of 15 meters or more
- produces cones
- some female cones can be huge
- sperm have flagella
- life cycle like that of conifers
Gnetophytes
- only gymnosperms to have vessels in their xylem; vessels are a particularly efficient conducting cell type that is a common feature of angiosperms
EX. Welwitschia from southwestern Africa
EX. Ephedra found worldwide; source of ephedrine - taken off market in 2004 because linked to strokes and heart attacks
Ginkgophytes
- only one species remains extant
- Ginkgo biloba has broad leaves that shed in fall
- sperm have flagella
- dioecious - separate male and female trees
- Fleshy covering of female seeds is very stinky like rancid butter
Angiosperms
- more than 250000 known species
- enclosed ovules within diploid tissue at time of pollination
- produce fruit (from carpel)
- origins are a mystery
Examples of Angiosperms
- Archaefructaceae (extinct family) may be sister clade, but debate continues
- Amborella trichopoda thought to be the closest living relative to the first angiosperm
Flowers
- house the gametophyte generation of angiosperms
- are modified stems that bear modified leaves
Flowers have four whorls
1) sepals - 3 to 5 and green, leaflike
2) petals - 3 to 5 and often colored
3) androecium = stamens
4) gynoecium = one or more carpels
Stamens produce
produce haploid pollen (the male gametophyte)
Carpel: 3 Major regions
- ovary, stigma, and style
- the carpel contains the female gametophyte
- the ovary becomes the fruit
Fruits are adapted for
dispersal
3 layers of ovary wall are:
- exocarp (outside)
- mesocarp (middle)
- endocarp (inside)
All 3 layers of ovary wall are called:
pericarp
* fates of these layers determines whether the fruit is fleshy or dry and hard
Fruits allow what to colonize large areas?
angiosperms
Fruits with fleshy coverings that are black, blue, or red are dispersed by what?
Birds and vertebrates
Fruits dispersed by birds and vertebrates have what?
A hard seed coat that is resistant to stomach acid or digestive enzymes
Fruits with hooked spines (burrs) are dispersed by what?
animal fur or human’s clothing
What buries acorns and nuts that could result in sprouting in the spring?
squirrels and other mammals
Fruits of maple, ash, and elm trees have what that aid in wind dispersal?
“wings”
Orchids have what that aids in wind dispersal?
dust like seeds
Dandelions have what that float on wind currents?
seeds with “parachutes”
What other plants have similar adaptions for wind dispersal like dandelions?
Milkweeds, cottonwood trees, willows, goat’s beard, and others
How do coconuts practice dispersal?
They can float in water to disperse to another island
Most species use flowers to attract pollinators and reproduce?
- nectarines
- scent
- some can be pollinated by wind, usually grass, trees, some flowers
The angiosperm life cycle includes:
double fertilization
Angiosperm Life Cycle
- Megaspore produces 8 haploid nuclei
- Female gametophyte consists of embryo sac and the 8 nuclei in only 7 cells
- Most important are the egg and the two polar nuclei in the single cell
- Pollen grain (after landing on receptive stigma) forms pollen tube toward embryo sac
- Two sperm pass through the tube
- One fuses with egg to form zygote
- Other sperm fuses with polar bodies to form triploid endosperm nucleus
- Endosperm will nourish the embryo
Monocots
- one cotyledon
- parallel veins
- scattered vascular tissue
- fibrous root system
- pollen grain with one opening
- floral organs in multiples of three
Eudicots
- two cotyledons
- net like veins
- vascular tissue arranged in a ring
- taproot usually present
- pollen grains with three openings
- floral organs usually in multiples of 4 or 5
In what ways do humans depend on seed plants?
food, wood, and many medicines
Why should we be concerned about the destruction of habitat across the world?
threatens the extinction of many plant species and the animal species they support
