Lecture 5 - Early plants

Question 1

First land plants, advantages and disadvantages of living on land

Answer 1

Viridiplantae (green plants) began to move to land and Rhodophytes remained stuck in the water.

The movement of Viridiplantae coincides with the increase in oxygen in the atmosphere.

A:
More oxygen, more space

D:
Less water availability, more difficult to sexually reproduce

Question 2

Bryophytes

Answer 2

The first type of plants: Contain no vascular tissue and didn’t have roots (Rhizoids)

Question 3

Examples of Bryophytes

Answer 3

Liverworts, hornworts, mosses

Question 4

Gametophyte

Answer 4

The generation of plants in which the gametes are produced and the plant is in a haploid phase.

This is the most dominant phase in bryophytes.

Question 5

Sporophyte

Answer 5

The generation of plants in which the spores are produced and the plant is in a diploid phase.

N/S: watch video

Question 6

Moss sporophytes

Answer 6

As the moss sporophytes were on land for longer, specific characteristics were favoured: a waxy cuticle (waterproof), vascular tissue, and stomata.

Question 7

gcvgtuvyu

Answer 7

difficutlies in SR, AP preferred (sporophy).

No difficulties in SR (Bryo), SP preferred (Gameto)

Question 8

First organism to have fossil evidence of sexual reproduction

Answer 8

Bangiomorpha pubescens around 1.2 billion years ago

Question 9

Cyanobacteria: what are examples and what do they have?

Answer 9

Blue-green algae: Chlorophyll a, phycobilisomes

Question 10

Viridiplantae: what is an example and what do they have?

Answer 10

Green algae: chlorophyll a and chlorophyll b

Question 11

Glaucophyta (algae): what do they have?

Answer 11

Chlorophyll a, phycobilisomes, chloroplast has wall

Question 12

Rhodophyta: what is an example and what do they have?

Answer 12

Red algae: chlorophyll a and phycobilisomes

Question 13

Chlorophyll a: what is it and what organisms have it?

Answer 13

The main type of chlorophyll. It is the most abundant chlorophyll, it has a large range of light that it absorbs (430-660nm) and the rate of absorption is high.

Almost every photosynthesising organism contains chlorophyll a

Question 14

Chlorophyll b: what is it and what organisms is it present in?

Answer 14

An accessory chlorophyll that has a low rate of absorption and a decent range of absorbed light (450-650nm)

It is only present in green plants and green algae

Question 15

Phycobilisomes: what are they, what do they do, and where are they located?

Answer 15

These are light-harvesting antennae that absorb the light that is not efficiently absorbed by chlorophyll and funnels light to photosystem II

It is attached to the stroma side of the thylakoid membranes of the cyanobacteria and red algae.

Question 16

One example of a green alga (C.r):

• Where can it be found?
• What key features does it have?
• What does mitosis produce and what state is it in most of the time?
• What may it do when stressed?
• How does mating work?

Answer 16

Chlamydomonas reinhardtii:

• Lives in fresh water and on soil
• Contains flagellum for movement
• Haploid most of the time and mitosis gives 4 daughter cells
• Sexual reproduction when stressed
• Gametophytes in 2 mating types
  mt+ and mt- (genetically set)

Question 17

Liverworts:

• Dominant gametophyte?
• Cells all one type?
• Roots?
• Water transport?
• Different sexes?
• Sporophyte?

Answer 17

Liverworts:

Dominant gametophyte - may grow as a plate (thalloid) or may be “leafy”

No, contains specialised cells, not all photosynthetic

Rhizoids grow down and absorb water

Primitive water transport

Gametophores grow up – male vs female, sperm swim from male gametophores (antheridia) to female ones (archegonia)

Sporophyte grows on gametophore

Question 18

Moss:

• Structure?⠀⠀⠀
• Water transport?
• Mineral obtaining method?
• Sporophyte?

Answer 18

Moss:

More complex structure, its “leaves” arranged in spirals with possible extensive branching

Simple water-conducting tissues

Maybe ombrotrophic

Sporophyte grows well above gametophyte and contains a waxy cuticle, vascular tissue and stomata

Question 19

Hornworts:

• Gametophyte?
• Sporophyte?
• Symbiosis?

Answer 19

Hornworts:

• Thalloid
• Similar features to moss, show a hint of independence
• With nitrogen fixers

Question 20

Ombrotrophic

Answer 20

Obtains minerals from the moisture in the air

Question 21

Minerotrophic

Answer 21

Obtains minerals from water running in the ground

Question 22

Gametophyte

Answer 22

The main stage of bryophytes.

Does all the “living” while completely independent of a sporophyte.

Haploid and so contains only one set of chromosomes

Question 23

Sporophytes

Answer 23

Used by plants to grow upwards and release spores to spread gametes of the organism around. These gametes would grow and eventually make sporophytes after interacting with another gametophyte, making a cycle.

Formed a waxy cuticle, vascular tissue, and stomata which are imperative for plants nowadays so, although sporophytes seem parasitic to gametophytes, sporophytes were somewhat helpful for evolution.