Lecture 5 - Early plants Flashcards
First land plants, advantages and disadvantages of living on land
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
Bryophytes
The first type of plants: Contain no vascular tissue and didn’t have roots (Rhizoids)
Examples of Bryophytes
Liverworts, hornworts, mosses
Gametophyte
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.
Sporophyte
The generation of plants in which the spores are produced and the plant is in a diploid phase.
N/S: watch video
Moss sporophytes
As the moss sporophytes were on land for longer, specific characteristics were favoured: a waxy cuticle (waterproof), vascular tissue, and stomata.
gcvgtuvyu
difficutlies in SR, AP preferred (sporophy).
No difficulties in SR (Bryo), SP preferred (Gameto)
First organism to have fossil evidence of sexual reproduction
Bangiomorpha pubescens around 1.2 billion years ago
Cyanobacteria: what are examples and what do they have?
Blue-green algae: Chlorophyll a, phycobilisomes
Viridiplantae: what is an example and what do they have?
Green algae: chlorophyll a and chlorophyll b
Glaucophyta (algae): what do they have?
Chlorophyll a, phycobilisomes, chloroplast has wall
Rhodophyta: what is an example and what do they have?
Red algae: chlorophyll a and phycobilisomes
Chlorophyll a: what is it and what organisms have it?
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
Chlorophyll b: what is it and what organisms is it present in?
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
Phycobilisomes: what are they, what do they do, and where are they located?
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.
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?
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)
Liverworts:
- Dominant gametophyte?
- Cells all one type?
- Roots?
- Water transport?
- Different sexes?
- Sporophyte?
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
Moss:
- Structure?⠀⠀⠀
- Water transport?
- Mineral obtaining method?
- Sporophyte?
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
Hornworts:
- Gametophyte?
- Sporophyte?
- Symbiosis?
Hornworts:
- Thalloid
- Similar features to moss, show a hint of independence
- With nitrogen fixers
Ombrotrophic
Obtains minerals from the moisture in the air
Minerotrophic
Obtains minerals from water running in the ground
Gametophyte
The main stage of bryophytes.
Does all the “living” while completely independent of a sporophyte.
Haploid and so contains only one set of chromosomes
Sporophytes
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.
