5. Chapter 30: Seed Plants Flashcards
What are the three main adaptations of angiosperms?
- the advent of the seed 2. reduction of the gametophyte 3. evolution of pollen
Define seed plants
vascular plants that produce seeds, an embryo packaged along with a store of food within a resistant coat
FYI: Seeds as food
- monoculture - a few seed crops dominate 2. single most important change 3. cultivation 10,000 years ago
List three ways in which the gametophytes of seed plants differ from ferns and bryophytes.
- microscopic 2. protected within the parental sporophyte 3. obtain nutrients from the parental sporophyte
Where is the gametophyte in pine tree? in other angiosperms?
- In the cone (female and male pollen cones; mainly diploid but tiny gametophyte inside) - In angiosperms (in ovaries which is in the flower)
What is the possible hypothesis for the adaptation to a dominant diploid sporophyte?
For harsh terrestrial environments, extra set of spare alleles in case one is damaged.
Why would the gametophyte continue to persist?
functions as a form of genetic screening - no alleles can hide in a haploid organism (all have to be working)
What does a seed consist of? What is the ploidy?
- sporophyte embryo (2N) 2. food supply (N) in angiosperm (3N) 3. protective coat (2N) (improved solution to resist harsh environments; move through space and time)
All seed plants are heterosporous. What does that mean?
produce two different types of sporangia and two types of spores (megaspores and microspores)
What does the megasporangia produce?
via meiosis produce megaspores (N) to form multicellular female (egg-containing) gametophytes (N)
What does the microsporangia produce?
via meiosis microspores (N) to form male (sperm-containing) gametophytes (N)
What does the ovule consist of? What is its ploidy?
Diploid (2N): consist of integuments. megaspore, and megasporangium
What does the zygote (egg fertilized by sperm) develop into? What does the ovule develop into?
sporophyte embryo; seed
What’s integuments?
derives a seed’s protective coat
Why is pollen an adaptation?
- eliminated water for fertilization (lack flagella) 2. covered with tough coat containing sporopollenin 3. carried by wind or animals (developed from microspore contained within microsporangium)
What are the most familiar phyla of gymnosperms? Other 3?
Conifers, the cone-bearing plants Ginko (single species: Gingko biloba), cycads, gnetophytes
How did the Earth change during the formation of the supercontinent Pangaea (Permian)?
- drier and warmer continental interiors 2. amphibians decreased in diversity, reptiles increased 3. horsetail ferns replaced by gymnosperms (suited to drier climate) 4. end of Permian (245 may) as boundary b/w Paleozoic and Mesozoic eras (mass extinction)
List some distinct characteristics of phylum coniferophyta. Examples?
- pollen. ovulues, seeds, born on cones, most evergreen, needle-shaped leaves, thick cuticle, stomata in pits, dominate Northern Hemisphere 2. pines, cedars, spruces, firs, etc. (BC: douglas fir, western red cedar, western hemlock) - largest and oldest organisms of Earth (heights of over 100m and 4,800 years old)
Commercial uses of wood (dead xylem tissue)?
lumber and paper BC Forestry Industry dominates - $16 billion/year - 46% provincial exports - 8% global forest products
8 steps reproduction in pine trees.
- produce pollen cones and ovulate cones 2. microsporangia (va meiosis) to microspores (N) to form pollen grains (male gametophytes) 3. many scales in ovulate cone, each with two ovules; megasporangium via meiosis to form megaspores (N) to female gametophyte to egg 4. Pollination via wind to ovulate cone 5. Pollen grain digest through megaspore ( can take >1 year) 6. Megaspore via meiosis produce 4 haploid cells, one will develop to megaspore 7. megaspore to female gametophyte containing two or three archegonia (ea. with egg) 8. eggs ready, two sperms developed in pollen tube => fertilization (only 1 embryo develops)
What does the pine seed consists of?
- embryo (new sporophyte) 2. food supply (from gametophyte tissue) 3. seed coat (from integument of parent)
Draw the gymnosperm life cycle.
What are angiosperms? What two clades are they divided into?
- vascular seed plants that produce flowers and fruits (most diverse). - Monocots (monophyletic) and the eudicots (includes original dicots; not monophyletic)
What is the defining reproductive adaptation for all angiosperms?
Flower, rely on insects and other animals to transfer pollen; some rely on random mechanism of wind pollination
What is a flower? Draw it.
a specialized shoot with four circles of modified leaves: sepals, petals, stamens and carpels. (“perfect” flower has both female and male reproductive organs)
What are the sepals?
base of the flower, modified leaves that enclose flower before it opens.
What are petals?
lie inside ring of sepals and often brightly coloured to attract animal pollinators
Are the sepals or petals involved in reproduction?
Not directly
What are stamens?
male reproductive organs; produce microspores that will give rise to gametophyte. (pollen) consist of filament and anther (where pollen is produced)
What are carpels?
female reproductive organs; produce megaspores that gives rise to female gametophyte (aka embryo sac)6 - sticky stigma receives pollen - style leads to ovary at the base of carpal - ovules and seeds protected within ovary
What is a fruit?
a mature ovary; various modifications help disperse seeds
6 Steps to angiosperms life cycle.
- anthers produce microspores that form male gametophyte (pollen) 2. ovules produce megaspores that form female gametophyte (embryo sac) 3. pollen carried to sticky stigma of carpal 4.when pollen tube reaches ovule two sperm discharge into female gametophyte 5. double fertilization - one sperm unites with egg to form zygote (2N), other fuses with two nuclei in centre cell of female gametophyte 6. zygote into sporophyte embryo packages with food reserve (3N) and surrounded by seed coat. (Embryo has one or two seed leaves - aka the cotyledons)
Draw the angiosperm life cycle.
What is the hypothesis for the function of double fertilization?
- synchronizes development of food storage in seed with development of embryo to prevent squandering nutrients on infertile ovules (sperm and eggs mature at different times to ensure cross pollination although some self pollinate)
What does the seed of an angiosperm consist of? What are the ploidy?
- Embryo (2N) 2. Endosperm (3N) 3. Seed coat (2N) from integuments (Ovary develops into fruit) (Seed germinates if environmental conditions are favourable)
What is coevolution?
mutual evolutionary influence between two species (i.e. insects responsible for plant diversity)
How do humans influence earth’s flora?
- Artificial selection: manipulate and select plants to maximize harvest (nearly all our food, grains aka grass fruits) - not the same as GMO (genetically modified organisms) 2. extinguishing plant species; extinction (plant diversity is nonrenewable resource
Why do humans depend on fruits?
depend for food production and oxygen release, building materials, medicines
