5. Sex Machine

Question 1

What were the 6 features of Chlamydomonas reinhardtii?

Answer 1

• Green alga
• Lives in fresh water & on soil
• Haploid most of the time
• Mitosis gives 4 daughter cells
• Gametophytes in 2 mating types
  mt+ and mt- (genetically set)
• Sexual reproduction when stressed
  (Garry Flew High 4 Gay Sex)

Question 2

Why and when does sexual reproduction in Chlamydomonas reinhardtii take place?

Answer 2

Sexual reproduction happens under stress –> forms zygote -> zygospore (only hatches when conditions are favourable again) –> meiosis & germination (haploid produced)
- when this happens –> recombination of genetic material occurs-> new combinations of genes (better adaptations)

Question 3

What is Alternation of Generations?

Answer 3

alternate between two different life stages, or generations, in their life cycle; a haploid stage called gametophyte and a diploid stage called sporophyte

Question 4

Why are Sea Lettuce Important?

Answer 4

• Because it has a Gametophyte (haploid; n) and sporophyte (diploid; 2n) generation.
• Both persist & grow as “seaweed” (look the same but aren’t)

Question 5

Why is Sushi important?

Answer 5

It shows alternation of generations, with distinct male & female structures (Gametophyte - plate like, Sporophyte - Filament)

Question 6

Why was the Cambrian Explosion Important?

Answer 6

• Led to the diversification of life, since there was now more atmospheric O2 present (forming ozone layer)
• UV light was harmful to plants getting closer to the land as it would break down cellular barriers & mechs.
• The formation of the ozone layer meant that less UV light would reach plants, so they would start moving onto land

Question 7

What are Viridiplantae?

Answer 7

-Unicellular
-Only plant to make it onto land (chlorophyll a & b)
- The ancestor of all current land plants

Question 8

What were the advantages & disadvantages of plants moving onto land?

Answer 8

Advantages:
- New/more space
- Higher CO2
Disadvantages:
- Lack of water
- Lack of Reproduction

Question 9

What did Viridiplantae diverge?

Answer 9

• Chlorophyta (Unicellular)
• Streptophyta (Unicellular)

Question 10

What did Streptophyta give rise to eventually and what advantages did they have?

Answer 10

Charophyta (Unicellular) & Embryophyta (Unicellular)
- They were land plants, meaning they could tolerate dryness (dry-tolerating green alga)
- These two gave rise to the Bryophytes (Multicellular)

Question 11

What plants make up the Bryophytes?

Answer 11

Liverworts
Mosses
Hornworts

Question 12

What are the features of Liverworts?

Answer 12

• live in moist/wet conditions
• Have rhizoids, which grow down
  & absorb water (primitive
  water transport)
  -Gametophyte of liverwort
  =called thalloid -> grows as
  Plate-like structure
  -Gametophore grow up from thalloid plate –> Male + Female (Haploid)
  -Sporophyte grows on gametophyte (diploid) (produced -> male sperm swims & fertilizes
  female)

Question 13

What are the features of Mosses?

Answer 13

-Have simple water conducting tissues
-Ombrotrophic = nutrients obtained solely from rainwater
-Sporophyte grows on & well above gametophyte
-Sporophyte: - produces haploid gen - Waxy cuticle waterproof
- VASCULAR TISSUE - Stomata

Question 14

What are the features of Hornworts?

Answer 14

-thalloid gametophyte
-sporophyte -> grows on & well above gametophyte (same as moss)
-blue-green appearance – due to cyanobacteria living in clefts (symbiosis with nitrogen fixer)