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Fundamentals of Plant Biology > Evolution of seed plants > Flashcards

Flashcards in Evolution of seed plants Deck (23)
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1
Q

What were the first plants to develop seed-like structures?

A

Seed ferns. Appeared 400 mya but are extinct

2
Q

What were the traits of progymnosperms?

A

Had spores instead of seeds, may have evolved from seed ferns. Branched off 390 mya

3
Q

When did the radiation of gymnosperms happen?

A

250 mya. They took over the world from the seedless vascular plants after the Permian extinction

4
Q

When did angiosperms appear in the fossil record?

A

130-150 mya

5
Q

When did pollen first appear in the fossil record?

A

250 mya

6
Q

What are the 2 reasons why pollen was a huge competitive advantage?

A
  1. No longer reliant on water for gamete exchange, pollen can go a lot further than just the neighbours, which increases genetic diversity
  2. Sperm is very easy to kill, and pollen isn’t
7
Q

What are the 3 components of a pollen grain?

A

Generative cell
Tube cell
Pollen wall

8
Q

What does the generative cell of pollen do?

A

The sperm cell that will fertilize the egg

9
Q

What does the tube cell of pollen do?

A

Transports the sperm cell to the egg

10
Q

What does the pollen wall do?

A

Mechanical stability, gas exchange, and provides a chemically inert environment

11
Q

What is the pollen wall made of that makes it so strong?

A

Partly made of sporopollenin, which is completely inert and basically indestructible

12
Q

Why are seeds an adaptive advantage over spores?

A

Embryo is protected and encased in a seed, and can be transported far from the parent plant. Seeds also last a lot longer than spores

13
Q

Where does the embryo get nutrients from in a gymnosperm seed?

A

Female gametophyte tissue

14
Q

What are 2 ways seeds are dispersed?

A

Wind: often have modifications to increase drag

Animal based

15
Q

How developed is the cuticle of seed plants?

A

Very complex and well developed. Covers the hypodermis. Much more complex than Monilophytes

16
Q

How many gymnosperms and angiosperms show secondary growth?

A

Only present in woody angiosperm species, but is in almost all gymnosperms

17
Q

How is having secondary growth an advantage for gymnosperms and angiosperms?

A

They can grow outwards to expand their stems, which allows them to grow taller and opens up possibilities for mechanical support

18
Q

What 7 traits are common to both gymnosperms and angiosperms?

A
Pollen is all that remains of the microgameteophyte
Fertilization occurs via the pollen tube
Use seeds for dispersal
Lacks antheridia
Heterosporous
Secondary cell walls
Woody species have secondary growth
19
Q

How are gymnosperms and angiosperms different in terms of ovule placement?

A

Gymnosperms: ovules are exposed
Angiosperms: ovules are enclosed in the carpel

20
Q

How are gymnosperms and angiosperms different in terms of pollination?

A

Gymnosperms: direct pollination by the pollen landing directly on the ovule. Often wind pollinated
Angiosperms: indirect pollination by the pollen landing on the stigma then the pollen tube growing down the style to fertilize the ovule. Often animal pollinated

21
Q

How are gymnosperms and angiosperms different in terms of fertilization?

A

Gymnosperms: single fertilization. One generative cell fertilizes the egg and the female gametophyte tissue provides nutrition to the embryo
Angiosperms: double fertilization. The generative cell splits into two before fertilizing the egg, one will fertilize the embryo and the other fertilizes the polar nuclei. The endosperm provides nutrition to the embryo

22
Q

How are gymnosperms and angiosperms different in terms of the megagametophyte?

A

Gymnosperms: larger megagametophyte with 2 archegonia each with one egg. Completely parasitic on the sporophyte at all life cycle stages
Angiosperms: 7 celled, 8 nucleated with no archegonia. Has a large cell in the middle with 2 polar nuclei, 3 antipodal cells, 2 synergids, and one egg cell

23
Q

How are gymnosperms and angiosperms different in terms of fruits?

A

Gymnosperms: no fruits
Angiosperms: fruit