Lecture 22 Flashcards
When did first land plants colonise earth?
Early Devonian scene (c. 450 million years ago)
What is the difference in evolution of plants and animals?
-Marine animals were highly evolved relative to plants prior to their movement onto land -Animals established their body plans prior to colonization of the land. -Land plants developed their body plans after they colonized terrestrial environments
Where did the first land plants get their nutrients from?
-first plants on land= nutritients from water still -evolution there happened quickly
What did the land plants evolved from?
land plants originally from a very specific type of green algae (know as we can tell where they got their chloroplast from
What is the evidence for green algae as the ancestors of land plants?
-similar pigments (chlorophyl A and B) -chloroplast structure -cell wall chemistry (cellulose) -both have starch as their storage material -style of division Coleochaete= the ancestor –due to comparing genomes -how they divide= moss and these very similar
What are the problems when living on land as opposed to living in water?
•Water balance • Gas exchange -Water transport • Structural Support • Reproduction
What adaptations did land plants develop to survive on land?
• Cuticle • Stomata; gas exchange • Vascular tissue; Xylem, lignin • Stems, roots, leaves • Secondary growth • Egg protected on female • Embryo protected in seed • Sporophyte dominance • Pollination cuticle= against drying out and sunscreen against UV -lignin= strenght so can be higher secondary growth= vascular cambium -fewer offspring more effort put into them diploid dominate in their lifecycle animals were already evolved so quick to pollinate when plants appeared
What is Rynia?
early land plant fossil -fossil fern -central region to give it strength= similar to plants more
In what sequence did cuticle, stomata, xylem and phloem, seeds, vascular cambium, flowers and double fertilization and xylem vessles= companion cells appear in lad plants?
What Features characterize the Mosses?
- No vascular tissue (therefore small plants)
- No roots • Thin cuticle appears
• Stomata appear
• Motile gametes (dependent
on free water)
• Gametophyte is the dominant
generation
• Soil crusts important in Australian ecosystems
- no way of pumping water= no vascular tissue
- cuticle= with sunscreen= protection against UV
- sperm swims to females= need water for it= water rich environment
only plants in the arctic regions= almost only liverworts and mosses
Decribe the sex cycle of green algae (Coleochaete)?
- look where sex and meiosis is.
- only diploid cell is zygote
Describe the life cycle of land plants.
- extra diploid cell sporophyte
- the zygote grows into multicellular organism that is diploid and then releases spores
When we see moss what is a sporophyte and gametophyte?
gametophyte= most of moss like that and most of life cycle in that part
Describe moss life cycle.
moss major form= gametophyte
girls produce eggs and boys sperm= so have to swim to it= have to be in water, so mosses have to be small and in water
-the moss after sex grows straight from the female bit
What is peat moss (sphangum) good for?
-• Hugely water absorbent
- Stores water and exchanges ions in Australian alpine and subalpine ecosystems
- Used as wound dressings in world war 1
- Major component of horticultural potting mix
- Fuel and grog!
- antiseptic properties
- whisky peat!
- Leaves consist of living photosynthetic cells and large, empty “hyaline” cells
Describe the life cycle of a fern.
-mostly diploid during its life
female= egg and argonium
- fertilisation still depends on water= has to swim
- look at the difference between ferns and mosses! possible exam q
What is the proprtion spent as diploid in green algae, mosses, ferns, gymnosperms and angiosperms?
In ferns=sporophyte major vegetative plant now! the majority of the life is spent as diploid
