Lecture Twenty One - Plant diversity III

Question 1

What was the first evidence of vascular plants?

Answer 1

Branching stems in plants.

Question 2

How is the plant life cycle (production of a sporophyte) advantagous to plants?

Answer 2

This life cycle including the production of a sporophyte is the key to how plants were able to collinise the land, from aquatic environments.

There are more spores which can be produced and therefore distributed.

Spores do not need water, covered sporopollenin, more suitable for land.

Question 3

Why did vascular tissues evolve?

Answer 3

For water conduction and structureal support to help plants grow taller, towards the sunlight.

Plants evolved to have a vascular cambium, which is a ring of meristomatic cells, these increase the gurth of a plant (the rings in a tree trunk) so that plants can grow taller towards the sunlight.

Question 4

What are the two theories for the evolution of leaves?

Answer 4

Enation theory - micrphylls (single vascular strand).

Leaves budded from stalk.

Telome theory - megaphylls or euphylls (reticular veins).

Leaves formed from conjoined stalks.

Question 5

Explain the trade off between gaining CO2 and losing water in plants?

Answer 5

To gain CO2, tissues must be exposed to the outside world.

In order to gain CO2, the stomata must open, thus losing water.

Question 6

How have angiosperms evolved to have an advantage over other plants?

Answer 6

Evolved to havea higher vein density.

This increases the hydrolic capacity of the plant (by more than double).

Increases the photosynthesis that can occur, as there is less water lost when the stomata opens to gain CO2.

This changed rainfall patters on the Earth, casuing greater rain fall.