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
• 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!
-Leaves consist of living photosynthetic cells and large, empty “hyaline” cells
What is a sporophyte?
is the diploid multicellular stage in the life cycle of a plant or alga. It develops from the zygote produced when a haploid egg cell is fertilized by a haploid sperm and each cell therefore has a double set of chromosomes, one set from each parent. All land plants, and most multicellular algae, have life cycles in which a multicellular diploid sporophyte phase alternates with a multicellular haploid gametophyte phase.
Why is Sphagnum in southeastern Australia?
In Victoria and NSW Sphagnum bogs are important alpine and sub- alpine ecosystems that play a crucial role in hydrology and ecology.
They are especially prone to damage, and are slow to recover from the effects of erosion caused by res and other disturbances
-water stored in it
-Sphagnum peat (turf) used as a fuel
What is a gemetophyte?
is a haploid multicellular adult stage in the alternation of generations during the life cycle of land plants and algae. It produces haploid gametes. It is produced from mitotic cell division of spores, which are produced by meiosis in sporophytes.
Gametophytes produce male or female gametes (or both), by mitosis. The female and male gametes are also called, respectively, egg cells and sperm cells. The fusion of male and female gametes produces a diploid zygote, which develops by repeated mitotic cell divisions into a multicellular sporophyte. Because sporophytes are the product of the fusion of two haploid gametes, these sporophyte cells are normally diploid, containing two sets of chromosomes. The mature sporophyte produces spores by a process called meiosis, in which the chromosome pairs are separated once again to form single sets. The spores are therefore once again haploid and develop into haploid gametophytes.
What are the characteristics of ferns?
• Roots and vascular tissue for water uptake and transport
• Cuticle (can function in drier environments)
• Sporophyte dominates
• Motile gametes (sexual reproduction reliant on free water
-can live in quite dry areas= some good cuticle
fiddler heads= the unfruling leaves= only in ferns
What is the dominant generation in the life cycle of a fern?
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 are the characteristics of treeferns?
• Restricted to sheltered
environments such as fern
• Trunks can grow up to 10 m
• Only the central core of the
trunk is the stem; the rest is a mass of roots and leaf- bases
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
What are the characteristics of water ferns?
• Several bizarre floating or aquatic ferns
• Azolla: common in Australia
• Marsilea (nardoo): a staple food of aborigines; Burke and Wills tried to survive on it at Coopers Creek
• Salvinia: a chronic tropical weed that has been effectively controlled by a weevil