Biodiversity in Animals

Biodiversity III: Plants

Oedogonium:

Figure labels (left to right): oogonium; antheridium

Q. What type of sexual reproduction occurs in Oedogonium? A. Oogamous sexual reproduction

Q. Is this species of Oedogonium

monoecious or dioecious? A. Monoecious if antheridia and oogonia on same filament

Dioecious if antheridia & oogonia on separate filaments

Q. What is the name given to the

male gametangium? A. Antheridium

Q. What is the function of zygospores? Are they haploid or diploid? A. Allows organism to survive during unfavourable conditions

Diploid

Q. What is the advanced reproductive characteristic illustrated by Oedogonium?

It is oogamous - gametes are not morphologically similar (male small and motile, female larger, non-motile)

Mosses

female thallus male thallus

(haploid) (haploid)

Q. Where are the gametangia located? A. At the tips of the male and female shoots

Q. Where would you expect to find the spore mother cells? A. In the capsule: they divide by MEIOSIS to produce haploid spores

Q. What is the ploidy of moss spores? A. Haploid

Q. What vegetative features found in plants does the moss have?

Rhizoids (root-like), body = thallus, and stalk (stem-like).

Q. What reproductive features found in plants does the moss have?

* Archegonium, antheridia, spores

* Alternation of generations. The haploid gametophyte is always dominant and the diploid sporophyte is always at least partially dependent on the gametophyte.

* Meiosis: produces spores

Q. What features do mosses have that indicate they are still "tied" to moist habitats?

* They lack a vascular system: so they rely on cell to cell diffusion for the movement of water and nutrients through the plant body. Mosses are mostly small plants which are restricted to aquatic or moist terrestrial environments.

* The plant body is a thallus and therefore lacks true roots, leaves and stems.

* Since the male gametes (sperm) swim, the plants are dependent on water for fertilization (ie for sexual reproduction)

Q. What features do mosses have that indicate that they are adapted to a terrestrial habitat?

Terrestrial adaptations:

a. A waxy cuticle to prevent water loss.

b. Stomata to regulate the exchange of gases.

c. Rhizoids serve to anchor the plant to the soil

d. Multicellular sex organs with an outer protective jacket of sterile cells (prevents gamete desiccation). Thus a true archegonium is developed [in place of the algal oogonium]  embryo develops within female gametangium (prevents embryo desiccation).

FERNS

Fern Gametophyte

Q. Where would you expect to find

the zygote? A. In the archegonium, following fertilization of the egg

Q. Why is the fern classified as a

vascular plant? A. Because its sporophyte generation has vascular tissue

Q. What is the function of the

annulus? A. It aids in spore dispersal

Q. Name one aquatic feature in

the life cycle of fern. A. Swimming male gametes (sperm)

Q. How are ferns more adapted to land than mosses?

* They all possess well-developed vascular systems, hence they can be large (no longer dependent

on diffusion to carry water and nutrients).

* Spores are small and light enough to be carried great distances by air currents. Upon reaching a suitable habitat, the spores germinate, usually during the following spring, and grow into a small heart-shaped gametophyte.

Conifers:

Q. Are conifers homosporous or

heterosporous? A. Heterosporous

Q. Where do the spores form?

A. Microspores in the pollen sacs (microsporangia)

Megaspores in the ovules (magasporangia)

Q. What is the embryo sac? A.

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