Deck 9: Diversity of Plant Life

Question 1

Compare the life cycle of a moss, a fern, a gymnosperm, and an angiosperm. What changes have taken place to the gametophyte generations in seed plants

Answer 1

The fist vascular plants lacked seeds; the two of seven phyla of living "seedless vascular plants" include the fens (phylum Pterophyta ) and the club mosses (phylum Lycophyta ). Ferns are the vascular seedless plants and they have both gametophyte and saprophyte individuals.
The haploid gametophyte produces eggs and sperm, sperm swim through water and fertilize the egg, the zygote grows into a saprophyte and it becomes much larger than the gametophyte. The saprophyte bears haploid spores and they float to the ground (through rhizomes, most ferns have rhizomes) where they germinate, growing into haploid gametophytes. These gametophytes are thin, small photosynthetic plants.
Gymnosperms were the first seed plants they produce two kinds of gametophytes. Male gametophytes are called pollen grains and female gametophyte is called ovum. Pollen is transferred to an ovule by wind, insects and other agents, thus fertilization occurs. This wind pollination of gymnosperms is inherently inefficient and led to the evolution of angiosperms.
Angiosperms are the flowering plants, in which the ovule is completely enclosed by sporophyte tissue. Flowers are the reproductive organs of the angiosperms, the attractive colours and shape of the flowers induce insects and other animals to carry the pollen. Parts of the flower develop into the seed and the fruit after fertilization.
In angiosperms, anthers produce microspores and ovules produce megaspores. The megaspore is a haploid spore formed in an ovule, which give rise to female gametophytes that produce eggs. Microspores are also haploid spores that give rise to pollen grains (male gametophytes).
The process of double fertilization led to the evolution of endosperm in angiosperms. The pollen grain of angiosperms contains two haploid sperm. The pollen begins to form a pollen tube upon the adherence to the stigma at the top of the carpel. The pollen tube grows down until it reaches the ovule in the ovary, and releases the two sperm into the ovary. One sperm fuses with the egg, forming the zygote that develops into the embryo.
The second sperm fuses with the nuclei to form a triploid (3n) endosperm cell. His cells divide rapidly than the zygotes, giving rise to nutritive endosperm tissue. The process if this fertilization with two sperm to produce a zygote and endosperm is called double fertilization.

Question 2

How does the three-domain system compare with the two-kingdom and five-kingdom systems

Answer 2

The three domain classification proposed by the Carl Woese in 1977. Based on this classification the living organisms are divided into three major domains, namely bacteria, Archaea and domains of eukaryote. In the domain eukaryote there are four kingdoms are present, namely Kingdom Fungi, Kingdom Plantae, Kingdom Animalia and Kingdom Animalia.
This Five kingdom classification proposed by Whitaker is made mainly based on the nutritional differences, for example, plantae are multicellular autotrophs, whereas animalia are multicellular heterotrophs and fungi are multicellular saprotrophs. The kingdoms of protista and monera include the unicellular organisms with simple cellular colonies. The five kingdom system proposed by Whitaker in 1969 includes the following,
1. Kingdom Monera
2. Kingdom Fungi
3. Kingdom Protista
4. Kingdom Plantae
5. Kingdom Animalia. 

Question 3

In the majority of land plants, the sporophyte is the dominant stage while the gametophyte is reduced, becoming completely dependent on the diploid phase in the most advanced divisions.
Suggest a reason why natural selection favored the dominance of the diploid sporophyte over the gametophyte.

Answer 3

NO ANSWER

Question 4

The discovery of the Wollemi pine emphasizes the value of national parks in the protection of natural habitats.
What are some of the other benefits of national parks

Question 5

Organisms traditionally called plants are now assigned to other kingdoms. Describe which groups have been reassigned and why.

Question 6

Describe the divisions of seed plants.

Question 7

What are the basic features of the ferns and lycophytes What is the economic impact of these groups, both living and fossil

Question 8

Describe the alternation of generations in vascular plants.

Question 9

Define sporangium, archegonium, antheridium, sporophyte , and gametophyte.

Question 10

Discuss the economic and ecological value of the gymnosperms.

Question 11

Describe the uses of peat moss.