Plant evolution - Biodiversity
When did plamnst first appear on earth
Aroud 500 mya meaning that first 3 billion years of earth there were no planst
This was due to harsh conditons that were present for large parts of the early earth for all life so there was only prokaryotic life
Can use ecological niches to see how planst used to live
Why was plant colonisation important
Altered the early atmosphere that had low level of oxygen as plants increased oxygen due to is a product of photosynthesis and also lowered CO2 levels so lowered the global temperature for more animals to survive
Created habitat and food source for animals
Planst provide way to harvest energy from the sun via photosynthesis and convert it to biomass so food
What were the charophytes
The first plant to evolve but was taking place in water in water based plants called charophytyes
In tidal area or pond there were plants that dry out due to have periods on land and were developing charctersitsc to allow them to fully survive outside of water over time
What is the evidenvce that land plants evolved from Charophytes
They share distinctive traits with land plants:
Multicellular organsims of eukaryotic cells
Chloroplast with both chlorphyll a+b
Cell wall containing cellulose like land plants
Perioxsosomes enzymes to minimise loss of organic compounds via photorespiration
Flagellated sperm in charophtye and land plnat have similar flagellated sperm structure
Cell divsion is the same
Gene sequencing of different genes and proteins between the 2 are similar
Both have Sporopollenin that protect zygote in charophyte and protect spores of land plants
How is celluolse produced for cell walls
Made by cellulose synthase complex that is arranged in rosettes with nenassary enzymes to produce cellulose
Multi-rosette group together in plasma membrane that can then extrude single cellulose strand to the cell wall
What are the challenges plants faced when moving to land
Water provie nutrient transport system
A way to reproduce
Structural support
Prevent dessication
Stable temperature
Buffer for solar radiation
What are land bases problems and solution for plants
Dessication - Lead to formation of waxy cuticle layer with stomata that allow water regulation with the guard cells, and prevent uncontrolled water loss as the stomata are regulated by tugor pressure
Water is suport medium= Cell wall has thickened due to extrac cellulose and the cross linking of carbohydrates
Obtaining nutrients - Formation of Rhizoid and root system with a symbiotic relation with mycorrhizae fungi that where plant with carbohydrate and in returin for gaining nitrogen
Assessing and transporting water- Development of vasculature with xylem and phloem
What are the main differnces between charophyte and land plants
Apical meristesm- Shoot and Root apical meristems, they are similar to stem cells due to undifferentiated unitl needed in either shoot or root of land plant
Multicellular gametangia - Gametangia is an organ where the gametes are formed that
Alternating generations in land plants - Produce a mega and micro spore in meiosis
Welled spores produced in sporangian - Tough sporpollenin wall protect spores from dessication
How are plant differentiated in phylas
Reproduction method, alternating generations whihc si the dominat the sporophtyic or gametophytic
Water relation so is there vacculature
Habitat
Seed prodcuing
Presence of leaves, roots, stems and flowers
What are the cyptograms
These are lower level plants that are seedless and spore bearing
They are non flowering and are dividied to 2 groups
Non vasculature cyptograms and vascualture cryptograms
What are the 3 types of non vasculature crytograms
Byrophytes
Hepatophyta
Anthocerophyta
What are the bryophytes
Mosses
Have a no compex vasculature so they are small in size
They rely on capillary movement of water and have Rhizoids due to no true roots
Usually dioecious so have male and female plants and there is distinctive alternating generations
The gametophytic is the dominant generation over the sporophytic
They are always ground hugging
What is the differenve between gametophytic and sporophytic
Gametophytic is haploid and will bear the gametes and happens via sexual reproduction
Sporophyte are diploid that have Seta + Capsule and are dependent on the gametophyte, they bear the spores and undergo meiosis
What is the life cycle of mosses
There is meisosis on sporangium to release haploid male and female cells tp
Male gametophyte release sperm from antheridia when rains that will then fertilise an egg from female gametophyte
This then forms a zygote that undergo mitosis to form young sporophyte that is sporophytic
How are mosses anchored to the ground
Gametophytes are anchored by Rhizoids
These are in mosses filament of cells but in loverwokrs they are long tubular single cells that have no role in water conduction
What are liverworts - Hepatophyta
Single thallus in some species with a more leafy appearance
They have similar life cycle so are gametophytic dominat
A sexual reproduction
What are Hornworts - Antherocerophytes
Symbiotic with N2 fixing blue green algae
They have 2 horns and grow from the base
What are Vacular Crytograms
Ferns, Horsetails and Club Mosses
These all have vascualor or conducting tissue
They have a dominant sporophytic generation and have rediced gametphyte called the prothallus
Allow plant to grow taller due to vascular
What are Ferns - Pteriodphyte
Have a sporophyte dominant generation
They have annulues thatr are dead cell filled with water that when water evaporate from them the annulus disort the outer wall and peel back to open the sporangium for spore release
Air comes out of the solution form,ing bubble and violent snap back of the annulus and so spores fire up into the air and are then caught by the wind, they need a damp envrioment
They are homosporous so no male or female
What is the fern life cycle
The prothallus produce eggs from the archegonium and sperm from the anteridium that are then combined so get fertilsiation in the gametophytic generation
In the sporophytic generation an enbryo is formed so get a young leaf formed that then develop into full adult fern leaf that have sorus which are cluster of sporangia
Spores are released and go back to prothallus
What are whisk ferns
13 species type with a high chromosme number and are able to obtain nutrients from deecaying matter
What are horsetails
They are an ancient species and were much larger in the carnoniferous oeriod but smaller todyay
In dry conditions they unfurl and disperse spores but in wet conditiosn they are tightly furled and no spore dispersal
They grow in rich silica soil and are homosporous
Dominant sporophttic generation and reduced gametophytic generation
What are club mosses
Flourished in the carboniferous period
Have true leaves and roots and some are heterophoreis species that are male and female
What is the significance of seedless vascular plants
Allowed development of vascular tissue, roots and leaves so greater photosynthesis, that lead to dramtic reduction in CO2 levels so then global cooling
What are Spermatophyta
These are seed bearing plants and there are 2 groups of them
Gymnospermsthat are cine bearing with unenclosed ovulues along with naked seeds
Angiosperms that are flowering plants with enclosed carpels
What genration is the dominant form
The final form of life is sporophytic domiant so they are 2n and diploid
In Gymonsperms they have female gametophyte in OIvulate cone and male gametophyte in pollen cone
In agiosperms they female gametophyte insde the female flowering part and male gametophyte in male part of the plant
How have spermatophyta evolved
Angiosperms evolved from the gynosperms 100 mya and are mow the domiant plant species on earth
Angiosperms have adapted different stratgies to adapt to many different niches
Why have seed plants become dominant
Embryo and food supply is surrounded by the protectoive coat
The sees is able to be transported away from the mother plant so they enter more niches
Sedd can stay viable for centuries if condtions not right they can lay dorman for long time and then germinate when conditions chnage to become favourable
How are seeds dispersed
By wind and animals
The seed pod will dry out and twist to create torsion and then cause explosion so see are propelled away
Plants are trying to disperse offspring seeds away from them so there is no competition between offspring annd parent for nutrients
What are the 5 main life cycle modifications
Heterspory so there is cross germination between planys and so cause a greate gene poll so drive evolution
Gametophyte is reduced and protected so can stay viable for very long time in the soil
Retention of female gametophyte on the sporophyte
Pollination to give the plant independence from free water and allow tghe plant to live in greater number of niches rather than just wet niche
Seed Habit so have embryo, endosperm and tetsa for protection
How has there been evolution toward gametophyte reduction
Moss and Bryophytes gave gametophyte dominated life style
Ferns and seedless vascular plants have a sporophyte dominted life cycle
Seed plants have sporophyte dominant lifecycle and macroscopic gametophytic generation
How will the Gametophyte develop within the sporophyte
This will allow moist enviroment so prevent dessication of the gametophyte
Protection from UV
Nutrient supplied from the sporophyte
What is heterosporous
All seed plants are heterosporous and so there is 1 type of spore that give rise to bisexual gametophyte
How are eggs produced in seed plants
Gymnosperms there are 1 integuments and in angiosperms there are 2 integuments
There are 8 nuclei and 7 cells
Integums are sporophytic tissue that envelope the megasporangium
How are microsporangium formed
Mosses and ferns produce flagellated sperm and require an aqueous environment to reach the egg
This limit the number of suitbale habitats
In seed plants the microspore develop in the pollen grain and so can use wind or animal to move further distances and can survive for longer time period , can enter more niches this way
What is the difference between spores and seeds
Spores: Can survive if local environment is non favourable, they are single cell so suceptible to UV and 1 genome and there is no nutrient supply
Seeds: Can survive for extened period of time in non local environments, they are multicellular so have a protective coat and have an endosperm so have a nutrient supply
How have Gymnosperms evolved
In the late devonain period some plant gained traits of seed bearing plants
The Archaeoptersi was the 1st plant to try and be seed bearing
First seed plant appeared 305 mya in a domiant seedless environment
As earth got warmer and drier it was more favourable for gymnosperms due to lack of water so gymnosperms dominated
What are the 4 phylum of Gynosperms
Ginkophyte
Cyadophyta
Gnetophyta
Conferophyta
What are the Ginkophyte
Dioecious plant so have seperate male and female plant
Female plant produce food unlike the males
Only 1 extant species called Ginko Biloba
What are Cycadophyta
The female cone split to reveal seeds and ovules
The male cone produce the pollen
There are 100 species and are an ancient plant group
What are the Gnetophyta
Closest relative of gymnosperm to angiosperm
Produce cones still with naked seeds that are male and female
69 species
What are Coniferophyta
There are 610 species and these are fern trees
They are the most succesful group with some pines being up to 5000 years old
What is the Pine lifecycle
It dominat is the sporophytic generation;
The Female ovule cone produces the megaspore and the m,ale pollen cone produce the microsporangium that undergo meiosis to produce pollen grains
The pollen and the megaspore form the megasporangium that then undergo meiosis to be gamatophytic
The megaspore produced has a female gametophyte develop in it to form the eggs that then combine with sperm nucleus from pollen to fertilse the egg
Then the fertile seed is then dispersed and can then go and grow into a fern tree
How have anigiosperm developed
These are classified as single phylum and are all flowering plants
Flowers produvce the microspore that develop ti the pollen grain in the male stamen
Produce the megaspore in the female carpel
Flowers need insects to tranport their seeds so are brighlty coloured to attract the insects
Some flowers may keep flower closed till they feel frequency of wingbeat of certain insect and then they open to allow insect access
Most of them are monoecious
What is the angiosperm lifecycle
Female ovule produce megaspore and male stamen produce male microsppre that is the pollen
Then the 2 combine so that the egg is fertilsed from the ovule
The the seed developed until is released and starts to germinate and develop into flower
What is double fertilisation
Pollen grains germinate after landing on the stigma and pollen grow towards the ovaries and can penetrate the micropyle
This increase chanve of making embyro and endosperm as the pollen discharge 2 sperm into female gametophyte
1 fertile egg will form the diploid zygoet that divide to form embryo
Other sperm fuse with 2 polar nuclei to form triplod cell that divdie to endosperm
What is the differnace between monocots and dicots
Monocot have - 1 cotlydon, Parrallel veins, scattered vascular tissue, fibrous root system, pollen grain with 1 opening and floral organs usally in tripletss
Dicots have - 2 cotlydons, veins are a network, vascular tissue in a ring, taproot are presentm pollen grain with 3 openings and floral organ in 4 or 5 multiples
How is the root protected
By a root cap that full of stem cells, and the cap protect the stem cells when root is penetrating the soil
How is the dicot embryo developed
Has a suspensor and is similor to the umbilical cord
It will connect the embryo to the parent and allow movement of water and food to the embryo
There is a series of cell divsion and lead to cell differentiation of cells in the embryo