Plants

Question 1

Which features of life cycle, structure and physiology are common to the protist green algae and land plants, and which unique to land plants?

Answer 1

Common to the protist green algae and land plants:
alternation of sporophyte and gametophyte generations
growth arising from specialised regions called apical meristems photosynthesis in plastids with chlorophyll a b and carotenoids energy stored as starch
requirement for light, water, mineral nutrients CO2 and oxygen cell walls of cellulose

Unique to plants:
an embryo arising from the union of male and female gametes that is protected and nourished by the female gametophyte or endosperm
the spores produced by the sporophytes are dispersed by air not water
multicellular sex organs with cellular walls that do not develop into gametes
Meiotic and mitotic nuclear divisions in which the nuclear membrane nucleoli breakdown in phosphase and centrioles are only seen at meiosis in cells develop into motile sperm

Question 2

In which major phyla the land plants is the sporophyte larger than the gametophyte and in which is it smaller?

Answer 2

Gametophyte larger: phyla - Hepatophyta, Bryophyta

Sporophyte larger: phyla - Filicophyta, Cycadophyta, Coniferophyta, Anthophyta

Question 3

Explain why bryophytes and ferns are mainly found in moist areas:

Answer 3

These motile sperm of these groups requires free water to swim to fertilise the egg in the archegonium. In addition Bryophytes lack roots and usually also a cuticle.

Question 4

Describe which parts of the cycad life style are diploid and which are haploid:

Answer 4

The palm like plant with its cones is the diploid sporophyte. In the cones inside the ovules there is a haploid female gametophyte. On the male plants the pollen is haploid. The zygote formed from fertilisation of the egg and the sperm is diploid.

Question 5

Compare the mode of sperm distribution and egg fertilisation in a pine and in a free-living fern gametophyte:

Answer 5

In free-living fern gametophyte - flagellated sperm are discharged from the antheridia and swim in free water to the neck of the archegonium,pass down the neck and the sperm and egg cells fuse, then the nuclei fuse.

In a pine - the winged pollen containing the sperm cells is distributed by wind and adheres to the micropyle of the ovule. A pollen tube grows to the neck of the archegonium delivering the sperm cells directly onto the surface of the egg cell. Egg and sperm cells fuse then the nuclei fuse.

Question 6

List the distinguishing characteristics of angiosperms:

Answer 6

Flowers, double fertilisation and endosperm, seed enclosed in an ovary.

Question 7

List the distinguishing characteristics of monocots:

Answer 7

One cotyledon (leaf of a seedling)
Fibrous root system
Main leaf vain linear 
Floral parts in multiples of 3
Vascular bundles of the stem scattered
No secondary xylem

Question 8

List the distinguishing characteristics of you eudicots:

Answer 8

2 cotyledons
Tap root
Leaf veins a network
Floral parts in multiples of 4 or 5
Vascular bundles in a ring
Secondary xylem (wood)

Question 9

Describe the structure and function of xylem:

Answer 9

Xylem has parenchyma, fibres, tracheids (and in almost all flowering plants) vessels. Water transport is in tracheids and vessels, elongated cells with walls strengthened with cellulose and lignin. Cells are dead at maturity and in vessels the end walls are eliminated during development. Function - water and nutrient transport in an upwards direction from roots to leaves.

Question 10

Describe the structure and function of phloem:

Answer 10

Phloem consists of parenchyma fibres, sieve tubes and companion cells. The sieve tubes lack a nucleus at maturity but have some cytoplasm and conduct sugars and other metabolites both upwards and downwards in strands that run through perforated sieve plates at the end of the cells. Companion cells functional in the loading and unloading of the sieve tubes.

Question 11

Explain how water and CO2 enter leaves the photosynthesis:

Answer 11

Water uptake by roots and transport in xylem, pulled to the leaves by the transpiration stream. CO2 through stomata (very slow diffusion through epidermis when stomata are closed)

Question 12

Explain how sugars produced by photosynthesis are transported through the plant body:

Answer 12

Sugars are transported by the phloem in sieve tubes, movement is in excess of diffusion and explained through the pressure flow hypothesis.

Question 13

Describe the ways in which flowering plants achieve the dispersal of pollen:

Answer 13

Wind, water (rarely), animals (mainly insects and birds but also mammals).

Question 14

Describe the ways in which flowering plants achieve dispersal of fruits and seeds:

Answer 14

Wind, water, animals (internally and externally), mainly birds and mammals but also reptiles and fish.