Lecture 3 part 2 Plant diversity lower land plants Flashcards
How are green land plants defined?
Cell structure & biochemistry
–Degree of vegetative complexity
–Type of life cycle
–Degree of complexity of their reproductive structures
What is the basic cell structure?
eukaryotic
What are the Chloroplast pgiments?
mainly chlorophylls & some carotenoids
What is the cell wall made out of?
made of cellulose
What is the typical storage material?
starch
What kind of flagella do Motile cells (Male gametes) have?
whiplash flagella
What growing points define Growth
–Called meristems
–Continue to divide indefinitely
–Plant body differentiates from the maturing daughter cells as the meristem grows away
Plant body shows differentiation into?
leaves & stems
What do some plant bodies lack?
Some lack this & body is flat & lobed
•Thallus
What does Elongated outgrowths increase?
the surface area in contact with the substrate (root hairs or rhizoids)
What phases do plants alternate between?
haploid phase
diploid phase
What is Haploid phase?
single set of chromosomes
What is diploid phase?
each nucleus contains 2 complete sets of chromosomes
What is the process that leads to the plant phase alternation?
fusion of gametes and meiosis.
What are gametes?
haploid unicellular reproductive bodies which fuse in pairs to form a diploid cell called a zygote
In most simple algae the vegetative plant is?
haploid
in most simple Algae the Zygote is?
diploid phase
For most animals the organism’s chromosomes are?
diploid & the gametes are haploid
What types of organism have an alternation of generations?
In advanced algae & all land plants
What are both haploid and diploid phases represented by?
distinctive vegetative organisms
What are the two distinct types of plants species consist of?
one haploid & one diploid
What is the order of the plant life cycle?
Haploid phase (Gametophyte) -> Fusion of gametes -> Diploid phase (sporophyte) -> Meiosis. Then back to Haploid phase
What is the order of the generalised life cycle of lower male land plants?
Multicellular vegetative haploid plant (gametophyte) -> Male sex organ(gametangium) -> antherozoids -> FUSION -> Zygote -> Multicellular vegetative diploid plant(sporophyte) -> Sporangium -> MEIOSIS -> SPORES
What is the order of the generalised life cycle of lower female land plants?
Multicellular vegetative haploid plant (gametophyte) -> Female sex organ (gametangium) -> egg -> FUSION -> Zygote -> Multicellular vegetative diploid plant(sporophyte) -> Sporangium -> MEIOSIS -> SPORES
How do haploid plants give rise to the diploid?
producing gametes–Called a gametophyte
These fuse in pairs to form a?
zygote
What does a zygote grow to form?
a diploid plant
What are the 2 kinds of gametes in all land plants?
–Male (small & motile)
–Female (large & non-motile)
What are the structure which give rise to gametes?
gametangia
Outline the main features of a diploid plant
-produces reproductive cells
–By meiosis
–Each grows to form a haploid plant without any fusion of pairs
–Unicellular propagule – called a spore
–Diploid plant is known as the sporophyte
•Spores are produced in a sporangium
What organisms do Byrophytes include?
–Mosses
–Liverworts
–Hornworts (Anthocerotae)
Outline the main features of a Bryophyta
- Multicellular
- Simple plants with some tissue differentiation
- Non-vascular plants
- Lack roots, have only slender rhizoids
- Have no woody parts
- Need water to complete their life cycle
- Susceptible to dessication
- Live in moist habitats
Give an example of the similarities between mosses and chlorophytes?
Especially between chlorophyte filaments & the moss protonema (juvenile moss from germinated spore)
What does the similarities between mosses and chlorophytes suggest?
Suggests that bryophytes evolved from certain chlorophytes
What chlorophylls do chloroplasts contain?
a & b
What kind of carotenoids do chloroplasts contain?
less abundant carotenoids (usually β carotene)•
What kind of alternation of generations does the life cycle of Bryophyta have?
Shows a heteromorphic alternation of generations
What is the dominant generation for Bryophyta?
Haploid gametophyte (maybe homo- or heterothallic) is the dominant generation
What part of the Ephemeral sporophyte is party or completely parasitic?
partly (or completely) parasitic on the gametophyte–Consists of a stalk bearing the spore capsule
What type of reproduction is common in Bryophyta?
Asexual reproduction
What does it mean by the Life cycle is an alternation of generation?
Both haploid & diploid phases are represented by distinct vegetative organisms
What does it mean by the Life cycle is heteromorphic?
Haploid & diploid plants are morphologically distinct from one another
Outline the main features of a Haploid plant
–Reproduces by gametes
–Known as gametophyte
–Diploid plant reproduces by spores
–Known as sporophyte
Outline the main features of the Bryophyte structure?
•Main plant body bears the gamete forming male organs (antheridia) & female organs (archegonia) (collectively known as gametangia (gamete forming organs)
–is known as the gametophyte
(Bryophyte structure) Antheridia give rise to?
the male gametes or antherozoids
(Bryophyte structure) Archegonia give rise to?
to the female gametes or eggs
Sporangia are reproductive organs which produce?
spores
Early summer sperm (antherozoids) released from the?
Antheridia
How do antherozoids (Summer sperm) get to a female archegonium?
swim in a film of water along the plant surface, enter a female archegonium & fertilise the oosphere, or egg
Is a oosphere haploid of diploid?
diploid
Is a gametophyte diploid or haploid?
Haploid
Are gametes haploid or diploid?
haploid
What does a oosphere undergo to become a fully formed sporophyte (A capsule on a seta (stalk)?
The oosphere undergoes mitosis, grows out of the archegonium & by quick growth in the following Feb/Mar develops into the fully formed sporophyte, a capsule on a seta (stalk)
How are elaters are formed?
Meiosis occurs within the capsule & haploid spores & elaters are formed
What happens to cause the spores to disperse?
The capsule splits, the elaters twist as they dry, dispersing the spores.
What happens after the spores are dispersed?
The spores germinate on damp soil & grow into a haploid gametophyte
What are the specialised methods of reproduction commonly developed in vegetation?
–Young leaf tips of foliose liverworts often bear small gemmae
–Some thallose liverworts produce gemmae cups on the dorsal surface
–Some mosses produce gemmae at the stem ends
–Some mosses produce bulbils (or other propagules) in the leaf axils
Outline the main characteristics of a Bryophytes
- Basically land plants–A few have adapted to aquatic environments
- Most species dry out readily
- Characteristic of moist or shady places
- Many mosses survive long periods of dessication–& can endure high temperatures in a dry dormant state
- Most Bryos thrive in low light intensities
- Many occur as epiphytes
- A large proportion prefer acid habitats, others may be calcicolous
What is the largest group of lower vascular plants?
Filicinae
How are Filicinae distinguised from other sub-divisions?
– their large leaves with complex branching systems
–Reproducing by spores
What is the general structure of a fern leaf?
Most fern leaves have forking veins which do not join together to form a net–Has a stele with xylem & phloem
Do ferns have an alternation of generations?
Yes
In ferns Sporophytes are?
dominant
In ferns Gametophytes are?
thalloid & much reduced
What are both Sporophytes and Gametophytes in Ferns?
Independant
How is Differentiation shown in sporophyte?
Differentiation is well marked in the sporophyte
How and where are spores produced in ferns?
Spores produced in sporangia, located in a sorus which usually has a protective indusium
Where are Seri located in ferns?
Sori located on underside of fern fronds
How is fertilisation undergone in ferns?
Fertilisation is by swimming of motile antherozoids from the antheridium to the archegonium & oosphere
Briefly describe Tracheophyta
Gametophyte plants – tiny & thallose–Or poorly differentiated underground plants–Is reduced & almost eliminated from the LC
- Have vascular tissue
- Plant is divided into root, stem & leaf
Briefly describe Filicinae
Plants in which the stem is an underground rhizome
- Leaves are large & dominate the stem–Often divided & resemble a system of branches–Veins rarely fuse together (no network)
- In most ferns the leaf unrolls from the bud
- Sporangia of ferns – usually borne in large numbers–Aggregated into sori–Each sorus develops under a protective flap (indusium)
How do you identify ferns?
- On number of times the frond branches
* Shape of the indusium & its attachment to the sorus
What kind of environment do ferns prefer?
prefer humid shaded habitats
- Relatively small number are adapted to dry/sunny conditions–Have reduced surfaces–Or a covering of hairs or scales
- To prevent loss of moisture
- Greatest number of fern spp. found in the tropics
What are Lichens?
- An association between a fungus & an alga or a cyanobacteria (a photosynthetic symbiont)
- Fungal lifestyle equivalent to parasitism or saprophytism
- Not a taxonomic group
- 1/5th of all fungi are parasitised
What is the current world-wide total of Lichens?
Current world-wide total = 13,500
How many Lichens are in GB and Ireland?
1,700
What does each Lichen contain?
a different fungus
How many photosynthetic partners are involved in lichen formation?
BUT only a small number of photosynthetic partners are involved in lichen formation–40 genera, 25 algal & 15 cyanobacterial
What has an influence on thallus development and architecture?
Algal partner
Taxonomy of lichen algae and cyanobacteria is?
Underdevelopment
How many partners come together to form a thallus?
Two
(Lichens - morphology) What are the 6 categories recognised?
–Fruticose (or shrubby)
–Foliose (flat & “leafy”)
–Crustose (underside of the thallus is closely attached to the substratum
- Squamulose (small scales)
- Placoid (elegant rosettes, lobed towards the margin)
- Crustose (true crusts – upper crust resembles crazy paving)
- Leprose – diffuse powdery mass of small granules
Explain Asexual reproduction in Lichens
•Asexual - Thallus fragmentation
–parts break off & are capable of growing into new plants
–Small outgrowths on the upper surface (isidia)
- Broken off when touched
- Production of powdery granules (soredia)
–Borne in patches on the upper surface or on edges of the thallus
Explain Sexual reproduction in Lichens
•Sexual – spores produced by perennial fruiting bodies on the thallus surface
What kinds of climates can Lichens survive in and how?
- Can tolerate complete drying out for long periods – for over a year
- Resume normal activity once re-wetted
- In the dry state they can survive extremes of heat & cold, but are incapable of any growth
- Take up water rapidly by absorbing it over their surface
- Some take up water from water vapour
What are Lichens exploited for by animals?
- Food
- Concealment
- Shelter
How does environmental pollution effect Lichens?
- Most are susceptible to environmental contamination
- Air pollution has the greatest effect on lichens
–Reduced to just a few spp. in towns
–Indicators of background air pollution are tolerant
–Most are harmed by pollution
