Lecture 2. Diversity of Life: Conquering the Land Flashcards
When did Earth form ?
4.6 billion years ago
What was Earths first atmosphere made up of ?
- Water vapor
- Little to no oxygen
- Nitrogen
- Carbon dioxide
- Methane
- Ammonia
- Hydrogen
How would you describe the early atmosphere ?
Reducing - organic compounds could have formed from simpler molecules
What was the earliest form of life ?
Bacteria which used energy from the sun
What facilitated the colonisation of land ?
Increase in oxygen
What are algae ?
- Eukaryote
- Photosynthetic
- Unicellular and multicellular
What are cyanobacteria ?
- Prokaryote
- Photosynthetic
- Unicellular and multicellular
What are bacteria ?
- Prokaryote
- Non photosynthetic
- Unicellular
When did the first prokaryotes appear ?
3.2 bya
When did the first single celled eukaryotes form ?
2.1 bya
When did the first multicellular eukaryotes form ?
1.2 bya
When was the Cambrian explosion ?
535-525 mya
What is the Cambrian explosion ?
A great increase in the diversity of animal forms
What happened 500 million years ago ?
Colonisation of land by fungi, plants and animals
Where did life evolve ?
In water
What are the environmental requirements for plants conquering land ?
- Formation of sizeable and stable near shore environments
- Development of soils
- Amelioration of atmosphere
- Suitable climatic conditions
What are the challenges for organisms abandoning life under water ?
- Desiccation of the body tissues, requiring some sort of waterproof coating
- Respiration of gaseous oxygen rather than oxygen dissolved in water
- Mechanical support (air is not as buoyant as water)
- Transport water and nutrients about plant
- Reduce need for water for reproduction
What prevents water loss ?
Waxy cuticle
What is the function of ANR gene ?
Required to tolerate extreme dessication in mosses
Where is the ANR gene not found ?
Flowering/vascular plants
What is cellulose the main constituent of ?
Cell walls and fibres
What is the function of lignin ?
Binds cells, fibres and vessels (wood)
What is the function of hemicellulose
Adds strength to cell walls
What is the stele ?
The central cylinder, inside the cortex, composed of the vascular tissue and associated tissues in roots and stems of vascular plants
Where were early land colonists found ?
Near shore
What protects from desiccation an UV light ?
Spore and seed walls
What were the first land plants ?
Green algae
What are the closest living relatives of the first land plants ?
Charopytes
What was the first vascular land plants ?
Cooksonia
What are pteridophytes ?
Vascular plants that reproduce with spores and developed large lobed leaves which are more efficient at capturing sunlight
What is the oldest known creature to have lived on land ?
Pneumodesmus newmani
What did tetrapods evolve from ?
Lobe finned fishes
What is the Tikaalik ?
The first vertebrate capable of crawling on land
What is oleanane ?
Produced by many common flowering plants as a defense against insects, fungi and various microbial invaders
What are paleosols ?
Ancient soils
