Biodiversity Flashcards
By counting the number of taxa what are you finding?
The species richness
What percentage of the worlds biomass is accounted for by plants?
90%
When do bryophytes start to invade the land?
The Ordovician - after the Cambrian explosion
What type of group are the non vascular plants?
Paraphyletic
Describe the alternation of generations in bryophytes
N haploid gametophyte dominant
- male and female sex organs
- sperm swims through film of water onto the egg and fertilises it
- egg becomes 2n diploid and grows into the sporophyte, produces the sporangia
- sporophyte is parasitic - cannot photosynthesise. Obtains its energy through the gametophyte
- sporophyte undergoes meiosis, single cells divide twice to form a tetrad - 4xn, these are released into the atmosphere. Drop onto the land and become a gametophyte
What does homosporous mean?
All spores are the same size and are all both male and female
Where are egg cells enclosed in bryophytes, describe this structure ?
Archegonium - single and flask shaped
What is meant by referring to the spermatozoids as zooidogamous?
Zooidogamous means the male gametes swim in a path of water to the female gametes
How many flagella do bryophyte sperm cells have
2
What makes up the wall of a bryophytes isospores?
Sporopollenin
What sort of size are bryophytes?
Generally very small
They have no lignin and hence they cannot have advanced water conducting cells
Why have bryophytes been able to exist almost everywhere?
Small spores are widely dispersed by wind
Can lose most of their water and still survive
Colonise bare rock e.g. Surtsey
Have phenolic compounds that protect from UV which enables them to live in polar regions, deserts and mountainous regions
Can be epiphytic
Although bryophytes have been found almost everywhere, what is the limitation to their invasion?
They must have a film of water over them to reproduce
What is an endolithic community?
One that lives under rocks
What are the big 5 problems for the movement of plants onto the terrestrial environment ?
Constant dehydration - xylem, cuticles, and stomata need to evolve
UV B radiation
Nutrient availability
Support - no longer supported by water, need lignin
Harder to reproduce - need to evolve ways of dispersing seeds
Give the order of bryophytes from most to least basal
Liverworts
Mosses
Hornworts
Give the main differences between bryophytes and tracheophytes
Bryophytes have no lignified tissues, and the gametophyte is dominant
Whilst tracheophytes have lignified conducting tissues, the sporophyte is dominant
For each bryophyte division give the number of species and generas
8000 species of liverworts (hepatics) in 400 genera
2000 species of mosses (musci) in 400 genera
100 species of hornworts (anthrocerotes) in 11 genera
What is meant by protonema?
The chain of cells that forms the earliest stage of the life cycle
Define dorsiventral
Flattened leaves having a distinct upper and lower surfaces as most leaves do
What is a thallus plant?
One in which the plant body is not differentiated into stem and leaves and lacks true roots and a vascular stem. E.g. Some liverworts
Where may you find oil bodies in a liverwort gametophyte?
Cytoplasm
On which side of a leafy liverwort are the leaves fully developed?
The dorsal side
Archegonia and antheridia, which is male and which is female
Archegonia is female
Antheridia is male
When the sex organs of a plant become umbrella shaped as they do in some liver worts what are they called? How do these develop?
Antheridophores - males
Archegoniphores - females
Develop from dichotomy ( repeated branching )
Where do antheridia lie in leafy liverworts? And the archegonium?
Antheridia in axils of leaves
Archegonium laterally or the tip of the shoot
What are elaters? And what isnt their purpose?
Elaters are made from cells undergoing meiosis, they are long cells that wiggle when dried to push all the spores out of the windpipe
What is true of all mosses gametophytes?
Leafy and multicellular rhizoids
What is meant by monoecious and dioecious?
Monoecious = plants that have sperm and eggs on the same gametophyte Dioecious = plants that have sperm and eggs on different gametophytes
Moses dont have elaters, what do they do to aid spore dispersal?
Use a peristome on the sporangium, these dry up and allow spores to release
What happens to the antheridia of mosses at maturity?
Its distinct lid opens and releases the spermocytes
From where does the moss sporophyte always grow from?
The apical cell of the gametophyte (tip)
What is a key step in the evolution of land plants from liverworts to mosses?
Obtaining a stomata
Stomata in mosses are not for gas exchange, what three things have the been considered to be for?
1) method of allowing sporangium to open
2) let water into the sporophyte
3) dry out the sporophyte to let spores leave
Describe a method of spore dispersal in mosses that involves the operculum
Sporophyte grows through the gametophyte and rips off the calyptra (protective layer to the archegonium) it then rips off the operculum as well, small section exposed that allows spores to escape through
What structure do hornworts take?
Thalloid structure,much of thallus is undifferentiated
Describe the sporophyte in hornworts
Remains inserted within the gametophyte, basal part surrounded by thallus tissue. Sporophytic tissue continuously produced by the basal meristem
Describe the evolutionary history of bryophytes
Mid ordivician - 475 mya, they first evolved from green algae
Don’t change for 40 million years
Early silurian (435mya) evolution of lignin, vascular plants dominant. Bryophytes moved to far corners
Mid Devonian 380 MYA
Trees evolve, epiphytes form and grow on trees
What is the most primitive form of living vascular plants?
Lycopsids
What are the major changes when moving from non vascular bryophytes to vascular lycopsids?
The 2n diploid sporophyte becomes dominant
Sporophyte has lignified conducting tissues enabling it to grow larger - explore more morphologies.
Are lycopsids hetro or homosporous?
Homo
Describe the alternation of generations in lycopsids
Sporophyte dominant
Cells in sporangia under go meiosis and form a tetrad that breaks apart to form spores.
Gametophyte grows from the spore and produces sex organs
Give features of the lycopsid order lycopodium
200 species in 3 genera Eliguate leaves Microphylls and sorophylls Homosporous Gametophyte can be surface or subterranean Conspicuous neck on archegonia
There is an order of lycopsid that has only one species, what is it and what are its features?
Phylloglossum
Multiflagellate spermatozoids
Forms tubours
What is the key difference within selaginella to the other lycopsids?
Heterosporous
Describe the alternation of generations in selaginella
Produces fewer larger spores rather than many smaller ones, falls down and produces a female gametophyte. Small spores produced in numbers, land and produce a male gametophyte
Why is heterospory advantageous?
Heterospory encourages outbreeding hence increases genetic diversity
Female mega spore has a large energy supply and hence can stay in one place for a large amount of time, meaning the species can live through dry periods. Plants can now invade in periodically damp environments and invade more of the planet
Where are the male and female spores kept within a selaginella?
Microsporangium holds the male microspores
Mega sporangium holds the female macrospores
When were lycopsids arborescent? How did this happen?
Carboniferous period
Very high oxygen levels, planet started to dry out in the permian from here they started to go extinct
How many species of selaginella are there?
700 in predominantly tropical areas
Which order of lycopsids is aquatic?
Isoetes/ stylites
Give the features of isoetes (type of lycopsid)
Aquatic
Heterosporus
Mega or micro sporangia
How does isoetes reproduce?
Spores released onto the surface of the lake
Male meets female, macrospore becomes denser and sink to the bottom
What is the only extant genus of sphenopsids?
Equistem - horsetail
In equisetum where is the sporangium found?
Top of the plant
Extant Sphenopsids are all homosporous. True or false
True but some fossil forms have been seen to be heterosporus
What is a spehnopsids epeltate?
The umbrella cone structure with the sporangia in the inside
Describe how sphenopsids attempt to encourage outbreeding
Gametophytes are released in flushes, females go first then males
What is the latin name for the plant group ferns?
Polypodiopsida
Describe the spermatoids in sphenopsids
Multiflagellate
Polypodiopsida are split into two groups what are these?
Eusporangiate - sporangium forms from two cells
Leptosporangiate - is where the sporangium forms from one cell
How do trunks of tree ferns form?
Leaves gradually infurl, roots grow arpund each one of these leaves, upon death the leaf leaves behind its base which forms the trunk
All ferns are _____sporous and the sporangia are on the _______side of the leaf
Homosporous
Underside
What is similar between the ferns and the bryophytes?
Both still need the film of water to reproduce
There is a very simple polypodiopsida that was mistaken for the most simple land plant what was it called? Why is it so basal?
Psilotales
All it does is bifocate and produce sporangia and it can be epiphytic
How long does the heart shaped gametophyte of ferns last for?
Not very long at all
Are ferns gametophyte or sporophyte dominant?
Sporophyte
There is one type of fern that is heterosporous what is it called? Where does it exist and how does it reproduce?
Hydropteridales
Aquatic
Megaspores float on surface and have hooks microspores get hooked and become trapped
When did ferns and sphenopsids arise? What did they occur after?
Arose in the late devonian. They came after the lycopsids
What did the ferns and sphenopsids diverge from? Give a brief description of this species
Trimerophytes
Bifurcating plant, sporangia occur on one sie
What is pseudomonopodial growth ?
Plants can bifocate but all stem grows in straight lines
What are the 5 major plant reproductive strategies
Bryophytes- gametophyte dominant homosporous Then sporophyte dominant homosporous Sporophyte dominant heterosporus Seed plants Flowering plants
Describe the alternation of generations in seed plants
Pollen grain is male and the megaspore - ovule - is female. The pollen grain lands in the ovule and forms a 2n zygote.
The ovule becomes a seed on fertilisation, gametophyte formed within the seed
Why is having seeds advantageous?
Removes the need for the film of water for reproduction, enables more invasions
Parents can look after daughters: when seed forms the tree can continue to provide food and water for the seed giving it more time to grow
When and from whom did the gymnosperms arise?
Trimerophytes in the devonian
Trimerophytes gave rise to both the gymnosperms and the sphenopsids seperately
When and as what do progymosperms appear in the fossil record? Where these hetro or homosporous?
Devonian as trees
Heterosporus plants
Give three examples of extinct seed plants (gymnosperms)
Pteridosperms - seed producing trees, evolves methods to keep the plant safe
Cordaites - carboniferohs forests similar to conifers
Glossopterids : seed plant in the permian
How many species of ginkgos are there? What is special about them?
1
They are a living fossil, thought to have gone extinct but then found in china
Ginkgos are diesius which means what?
They have two “houses” seperate male and female plants
Which gender tree produces vomit smelling slime
Female
How many genera in how many species are there in cycads?
80 species in 12 genera
How long can cycads live? Where are they found? In what respect are they similar to ferns?
Large amount of time, up to 400 years
Tend to grow in the tropics
Leaves die and leave behind the trunk
Because cycads often produce _______ they have become endangered due to agriculture. However because they can __________ populations can be restored from relatively low numbers
Toxic seeds
Change sex
Which gender of cycad holds the cones
Both
The male opens its cone to release pollen
The female opens its cone to enable pollen to swirl around within it
What is meant by conifer?
Cone plant
How is the pollen of the conifers adapted?
Air sacs enable it to fly and float
Describe the female cone in a conifer
Female opens up and exposes the ovule, pollen sucked in and fertilises. Cone seals up for upto 1 year to help the seed develop.
Conifer means cone plant but what is wrong with this name?
Some conifers produce berries e.g. The yew tree.
Analysis of the berries ontogeny they seem to be modified cones with a single ovule
Gnetales have 3 genera which are?
Welwitshia
Ephedra
Gnetum
Give the extant orders of gymnosperms
Ginkgos
Cycads
Conifers
Gnetales
What is meant by mosaic evolution?
Different bits of the plant can evolve without effecting other parts
What are 9 important features of land plants?
Simple organisms with around 40 cell types
Essentially sedentary
Plants can regenerate
Reproductive propagules can last for a large amount of time
Can easily hybrize
Often form polyploids - rapid speciation
Asexual reproduction
Mosaic evolution
Small populations can exist successfully
Plants rarely go _______ . Liverworts have remained unchanged since ___________ lycopodium from _____MYA resemble ____________. And _______ have been around for 240mYA
Extinct Mid ordovician 280mya Lycopsids Cycads and ginkgos
Why did Carboniferous forests last for much longer in china?
China didnt move as much due to tectonic movement
What three categories of changes drive plant evolution?
Environmental change - climate change, techtonic movement
Coevolution - mycorrhizal fungus, animals eating plants, plants eating insects
Freak events - polyploidy
Where are seeds held in angiosperms?
An ovary - fruit
Angisperms have __________ species which makes up ___ of the worlds plant species
250,000
90%
Describe the female sex organs of a angiosperm
Pistil or carpel
Which is made of the pollen acceptor - the stigma and the style - the stigma supporter
Describe the male sex organ in angiosperms
Stamen with an anther - pollen producer
Darwin called the origin of angiosperm an _______________, because they suddenly appear in the fossil record in the ___________. They became the dominant vegetation by __________.
Abominable mystery
Mesozoic era
93.6 MYA
What are the best current guess for where angiosperms arose from?
Cycads or pteridosperms
What percentage of angiosperms are either monocots or eudicots?
98%
How many monocot species arw there? How many orchids ?
60,000 monocots, 20,000 of which are orchids
The cot part of monocot or eudicot means what?
Cotyledon = seed leaves, formed within the seeds and are identical to the maternal leaves
Describe the tissues differences between monocots and eudicots
Monocots have parallel tissues
Eudicots have net tissue
Describe stomata in eudicots and monocots
Monocots have stomata in lines on both surfaces
Eudicots have them scattered and only on the underside
Describe vascular bundles in monocots and eudicots and explain how this allows for eudicots larger size
Monocots - vascular bundle throughout the cell, prevents cambium production which means they cant produce wood
Eudicots have a vascular bundle in a continuous ring at the surface allows them to produce cambium and hence can support themselves at much greater heights
What are the different roots in monocots and eudicots? What are the pros pf each?
Monocts are fibrous - adventurous root system, explore more but near the surface
Dicots have taproots - less adventurous but goes much further down