30 Plant Diversity: The Evolution of Seed Plants Flashcards
What is the basic purpose of a seed?
To contain the embryo, its food supply, and a protective coat
Why are seeds advantageous over the methods employed by seedless plants?
- Does not need water for sperm to swim through
- Larger dispersal radius
- Allows for dormancy
Why are ferns not seen in the desert?
Their sperm needs water to travel between plants
Why are mosses typically found in moist conditions?
Their sperm needs water to travel between plants
In what organisms are the gametophytes the dominant life stage?
Mosses and other bryophytes
In what organisms are the sporophytes the dominant life stage?
Ferns and other seedless vascular plants, gymnosperms and angiosperms.
Describe the gametophytes of mosses and other nonvascular plants in terms of size and dependance.
Dominant
Describe the gametophytes of ferns and other seedless plants in terms of size and dependance.
Reduced, independent (photosynthetic and free-living)
Describe the gametophytes of seed plants (gymnosperms and angiosperms) in terms of size and dependance.
Reduced (usually microscopic), dependent on surrounding sporophyte tissue for nutrition
Describe the sporophytes of mosses and other nonvascular plants in terms of size and dependance.
Reduced, dependent on gametophyte for nutrition
Describe the sporophytes of ferns and other seedless vascular plants in terms of size and dependance.
Dominant
Describe the sporophytes of seed plants (angiosperms and gymnosperms) in terms of size and dependance.
Dominant
What is most common in seedless plants: heterospory or homospory?
Most seedless plants, including terms, are homosporous
Are seed plants homosporous or heterosporous?
All are heterosporous as they produce separate sperm (pollen) and eggs (ovules)
What produces megaspores?
Megasporangia
What are the structure of a seed in terms of whether they are derived from sporophytic or gametophyte tissue?
The seed coat is derived from the integument and thus the “grandparent generation” - hence 3 generations in a seed
The spore wall is surrounded by remnants of the megasporangium (sporophyte)
The food supply of the seed is from female gametophyte tissue.
The embryo in a seed is the new sporophyte.
What is the tough coating of the seed called?
The seed coat
What is the spore wall?
A thin layer between the seed coat and the interior of the seed
What is the purpose of the integument?
It protects the unfertilised ovule
What are the early gymnosperms called?
Progymnosperms
What are progymnosperms?
Species that are are transitional species between seedless vascular.
For example some were tall but had fern like leaves and were heterosporous but did not produce seeds
What does ‘paleozoic’ literally mean?
Early life
What does ‘mesozoic’ literally mean?
Middle life
What are the phyla of gymnosperms?
Cycadophyta, ginkgophyta, gnetophyta and coniferophyta.
What are plants in cycadophyta like?
They have large cones and palm like leaves
What group of plants are plasm trees?
Angiosperms
What gymnosperm phylum was particularly present at the time of the dinosaurs?
Cycadophyta
Into what groups are cycads classified?
They are gymnosperms in the phylum Cycadophyta
What are organisms in the phylum cycadophyta called?
Cycads
In what phylum are cycads?
Cycadophyta
What are organisms in Ginkgophyta?
There is only one extant species. It is a deciduous tree with fan like leaves that turn golden
What is the sole species of Ginkophyta called?
Ginkgo bilboa
What are species in the Ginkgophyta phylum called?
Ginkgos
In what phylum are ginkgos?
Ginkgophyta
What are plants in the gnetophyta phylum called?
Gnetophytes
In what phylum are gnetophytes?
Gnetophyta
What are gnetophytes divided into?
Three genera: Gnetum, ephedra and welwitchisa
What does genera refer to?
It is the plural of genus
What is the plural of genus?
Genera
What is gnetum?
A genus of gnetophyta
What is ephedra?
A genus of gnetophyta
What is welwitschia?
A genus of gnetophyta
What are the properties of plants in the welwitschia genus?
This consists of a single species of desert plant with huge leaves
What are the properties of plants in the ephedra genus?
This genus includes about 40 species that inhabit arid regions worldwide.
What is ‘ephedrine’?
A medicine produced by desert shrubs in the Ephedra genus (gnetophyta phylum) as a decongestant
What are the properties of plants in the gnetum genus?
This genus includes about 35 species of tropical trees, shrubs, and vines, mainly native to Africa and Asia.
Their leaves look similar to those of flowering plants, and their seeds look somewhat like fruits.
When do most conifers lose their leaves?
They don’t: most are evergreen
In what phylum are conifers?
Coniferophyta
In what phylum are juniper trees?
Coniferophyta (they are conifers)
In what phylum are pine trees?
Coniferophyta (they are conifers)
In what phylum are sequoia trees?
Coniferophyta (they are conifers)
What are trees in the coniferophyta phylum called?
Conifers
What is the reproductive life cycle of a pine?
Each tree produces two type of cones: ovulate cones and pollen cones.
In the pollen cones microsporocytes produce haploid microspores by meiosis. A microspore develops into a pollen grain (a male gametophyte enclosed within the pollen wall).
The ovulate cone has many scales, each has two ovules.
Pollination occurs when a pollen grain reaches the ovule. The pollen grain then germinates, forming a pollen tube that grows to the megasporangium.
As the pollen tube grows the megasporocyte undergoes meiosis to produced 4 haploid cells, one survives as a megaspore. The megaspore develops into a female gametophyte multiple archegonia, each becomes an egg.
Only now that the eggs are mature does fertilisation occur as the sperm fuses with the eggs.
All eggs may be fertilized, but usually only one zygote develops into an embryo. The ovule becomes a seed, consisting of an embryo, food supply, and seed coat.
What is a sepal?
The small leaf-like structure at the base of the flower
What is nutritious tissue of fruit called?
The pericarp
What is pericarp?
The fleshy tissue in a fruit that develops from the swollen ovule’s wall.
For example the mainly fleshy bit of an apple
What is sugar rich yellow tissue of an apple an example of?
It is pericarp.
What is the female gametophyte called?
The embryo sac
What is the transfer of pollen form one plant to another called?
Cross-pollination
What is cross-pollination?
When pollen travels between different individuals.d
What are the derived traits of seed plants?
Reduced gametophytes - microscopic male and female gametophytes are nourished and protected by the sporophyte
Heterospory
Ovules
Pollen: makes water unnecessary for fertilisation
Seeds: survive better than unprotected spores, can travel farther
What does a male gametophyte contain?
A generative cell that divides to form two sperm and a tube cell that forms the pollen tube
What is a ‘generative cell’?
A cell in the male gametophyte that divides to form two sperm cells.
What is the process by which triploid endosperm is formed called?
Double fertilisation
How exactly does double fertilisation occur?
One sperm (not both) fuses with two polar nuclei
What are the stages of the reproductive lifecycle of an angiosperm?
On the anther, each microsporangium contains microsporocytes that divide by meiosis to produce microspores that become pollen grains.
In the megasporangium of each ovule, the megasporocyte divides by meiosis, producing four megaspores. One survives and forms a female gametophyte.
After pollination the two sperms cells are discharged into the ovule.
Double fertilization occurs. One sperm fertilizes the egg, forming a zygote. The other sperm fertilises the central cell (which has two nuclei), forming the endosperm.
What does ’central cell’ refer to?
This refer to the polar nuclei at the centre of an ovule.
This cell has two nuclei so when it fuses with a sperm a triploid endosperm results.
What is the structure of a pollen grain and their purposes?
The generative cell of the gametophyte will divide, forming two sperm. The tube cell will produce the pollen tube.
What does ‘eudicots’ refer to?
“True dicots”
What are angiosperms divided into?
‘Basal angiosperms’, ‘magnolids’, ‘monocots’ and ‘eudicots’
What type of angiosperm are water lilies?
Basal angiosperm
What type of angiosperm are magnolias?
Magnoliids
What type of angiosperm are black pepper plants?
Magnoliids
How do monocots and eudicots differ?
Monocots have one cotyledon, eudicots have two
Monocots have parallel leaf veins, in eudicots they are branched
Stems in monocots have scattered vascular tissue, in eudicots it is arranged in a ring
Monocots have fibrous roots, eudicots have a main taproot
Monocots have pollen grains with one opening, in eudicots there are three
In monocots floral organs i.e. petals are often arranged in multiples of three. In eudicots they are arranged in multiples of four or five.
