Plants Invade The Land

Question 1

Did animals establish their body plans prior to or after colonisation of the land?

Answer 1

Prior to.

Question 2

Did land plants develop their body plans prior to or after their colonised terrestrial environments?

Answer 2

After.

Question 3

What groups all land plants together phylogenetically?

Answer 3

They are unified by a primary endosymbiotic event.

Question 4

Why are the Charaphyte green algae said to closest relatives of land plants?

Answer 4

Both form a phragmoplast during mitosis.

Both also have an open mitotic spindle (nuclear envelope disappears)

Both are also multicellular.

Question 5

What is a phragmoplast?

Answer 5

A group of microtubules that forms between two daughter nuclei.

Question 6

Compare how gas exchange occurs with photosynthetic organisms in aquatic environments vs land plants.

Answer 6

Photosynthetic organisms in aquatic environments get carbon dioxide dissolved in water

Land plants get carbon dioxide from atmosphere

Question 7

Compare water transport methods between aquatic plants and land plants.

Answer 7

Aquatic plants: no water transport system bc whole plant surface is absorbent

Land plants: NEED a water transport system

Question 8

Compare structural support between aquatic and land plants.

Answer 8

Aquatic plants rely on buoyancy for support e.g green algae

Land plants require structural support in free air.

Question 9

Compare reproductive methods between aquatic and land plants.

Answer 9

Aquatic plants have motile gametes that have flagella and move through water

Land plants must evolve way to reproduce without relying on water.

Question 10

Why was the cuticle an important adaptation for land plants?

Answer 10

Waxy and hydrophobic surface on plant that protects against water loss, impermeable to gas, UV radiation and pathogens.

Question 11

Why was the stomata an important adaptation for land plants?

Answer 11

Stomata: pore in between two guard cells located in the plant epidermis (underside of leaves)

Regulates water loss and gas exchange, opens to allow CO2 in.

Question 12

Why was vascular tissue (xylem, lignin cell walls) a key adaptation for land plants?

Answer 12

Xylem vessels allow for efficient movement of water from one part of the plant to another.

Lignin cell walls strengthens xylem vessels so they don’t collapse under hydrostatic pressure when water moves through them.

Question 13

Why was differentiation into stems, roots and leaves an important adaptation for land plants?

Answer 13

Allows for division of labour within the plant

Question 14

Why is secondary growth of woody tissues (vascular cambium, meristem) an important adaptation for land plants?

Answer 14

Enables plants to grow larger

Improves capacity of plant to move water up toward canopy up top

Question 15

State 3 reproductive adaptations for land plants and describe why they are important.

Answer 15

1. Egg protected on female
2. Embryo protected in seed
3. Sporophyte dominance

Embryo protected in seed ensures that seed is provided with nutrients and can remain dormant for years so it can germinate in favourable conditions.

Question 16

Describe why pollination is a key adaptation for land plants.

Answer 16

Delivers sperm cells directly to egg, no water required.

Question 17

State key features that evolved in land plants in chronological order form earliest to most recent.

Answer 17

1. Cuticle, embryo
2. Stomata
3. Phloem, lignin, tracheids
4. Seeds, pollen grains, secondary wood
5. Non flagellate sperm
6. Carpel (flowering plants)

Question 18

What are the most primitive land plants?

Answer 18

Liverworts and mosses.

Question 19

What are the 3 lineages of non vascular plants?

Answer 19

Liverworts, hornworts, mosses

Question 20

Why were the earliest plant fossils of spores?

Answer 20

Because they were impregnated with sporopollenin (tough coating)

Question 21

State the main features that characterise the mosses.

Answer 21

• no vascular tissue (therefore small plants)
• no roots (rhizoids for anchoring)
• thin cuticle (quickly dry out)
• stomata
• motile gametes

Question 22

What is the dominant generation in mosses?

Answer 22

Gametophyte (1N haploid)

Question 23

What is Coleochaete?

Answer 23

Green algae most closely related to land plants

Question 24

Are Coleochaete sperm motile or immotile?

Answer 24

Motile, swim in water

Question 25

What is karyogamy?

Answer 25

Process in reproduction where haploid gametes fuse to give the diploid cell.

Question 26

Describe the steps in the Coleochaete life cycle.

Answer 26

1. Gametophyte (n) produces gametes by mitosis
2. Motile sperm cells swim around until they fuse with an egg cell retained on parent plant
3. Karyogamy to form diploid zygote (2n)
4. Zygote immediately undergoes meiosis to produce spores
5. Spores germinate into gametophyte.

Question 27

Describe how the land plant life cycle differs from Coleochaete.

Answer 27

Exact same EXCEPT the zygote does not immediately undergo meiosis.

Instead, the zygote undergoes mitotic divisions to produce a multicellular sporophyte.

This sporophyte then undergoes meiosis to produce spores which germinate into the gametophyte.

Question 28

All features that we associated with plant life on land is associated with what generation?

Answer 28

The sporophyte generation.

Question 29

What is the moss life cycle reliant on? Why?

Answer 29

Water. Motile sperm.

Question 30

what is the dominant generation of the moss life cycle?

Answer 30

Gametophyte.

Question 31

Describe how the moss life cycle differs from Coleochaete.

Answer 31

Moss life cycle has ALTERNATION of generations - gametophyte is dominant and sporophyte is ephemeral stage.

Question 32

Describe the relationship between sporophyte and gametophyte generation in mosses.

Answer 32

Sporophyte is attached to gametophyte and ARISES from the gametophyte. Sporophyte is also parasitic on the gametophyte.

Question 33

Describe the stages of the moss life cycle.

Answer 33

1. Sperm swims to egg cell, jams itself down top f neck of egg cell, once it reaches bottom, produces zygote.
2. Zygote/sporophyte produces capsule where meiosis takes place, also embeds itself in gametophyte.
3. After meiosis, moss sheds spores. This is a dehiscence mechanism.
4. Capsule has pixie cap with teeth form which spores filter out.
5. Once spores land on ground they’ll germinate into gametophytes.

Question 34

Describe the main characteristic of peat moss (Sphagnum).

Answer 34

• hugely water absorbent

- leaves consist of large empty HYALINE cells with pores that soak up water

Question 35

What adaptations make the ferns more suited to life on land than the mosses?

Answer 35

• first plant with vascular tissue for water and transport
• differentiation into roots, stems and leaves
• sporophyte dominates life cycle

Question 36

Describe fern sperm cells. What was this inherited from?

Answer 36

Motile gametes, primitive therefore inherited from green algae.

Question 37

What generation dominates the fern life cycle?

Answer 37

Sporophyte

Question 38

Describe the life cycle of a fern.

Answer 38

1. Sperm from antheridium fuses with egg in archegonium, forms embryo.
2. Embryo forms 2N zygote which becomes sporophyte.
3. Sporophyte (leafy part) grows from gametophyte
4. Older sporophyte becomes frond.
5. Gametophyte is shed once sporophyte is able to photosynthesise.
6. At base of frond on underside of leaf is sporangia which is where meiosis takes place to produce haploid spores.
7. Spores are shed and produce gametophyte.

Question 39

When does the gametophyte generation occur in ferns? What about the sporophyte generation?

Answer 39

Sporophyte generation (2N) occurs when zygote is formed (karyogamy).

Gametophyte generation (1N) occurs when meiosis occurs as spores are shed.

Question 40

What is the sporophyte initially dependent on for nutrients?

Answer 40

The gametophyte.

Question 41

Compare green algae, mosses and ferns in terms of the alternation of generations or lack thereof.

Answer 41

Green algae: only one diploid cell the zygote, gametophyte dominant

Mosses: gametophyte still dominant, sporophyte more complex

Ferns: sporophyte now dominates, gametophyte is more basic, sporophyte and gametophyte are free-living.