Transcript Chapter 3. Multicellular Diversity: Algae and Plants - Blyth

Chapter 3. Multicellular Diversity:
Algae, Plants and Fungi
Lesson 5.
Learning Goals
Algae
• Simple, aquatic, plant-like organisms that contain chlorophyll
• Lack the leaves, roots, stems and water-conducting materials
of plants
• Range in size (single cells to giant seaweeds 60 m in length)
• Algae is not a proper taxonomic group
• Debate amongst scientists whether they belong to Kingdom
Prosista or Plantae
• They have been on the earth for about 2 billion years and
scientists are still discovering new species
Algae
• Algae are classified into six different phyla based on the type
of chloroplasts and pigments they contain.
• Have different types of chlorophylls and other pigments,
suggests that chloroplast-containing cells evolved three times.
• Three phyla are unicellular
– Dinoflagellates
– Diatoms
– euglenoids
• three are multi-cellular
– Green, red and brown algae
• Other differences include the chemistry of their cell walls, the
number and position of flagella (if any) and the form that food
reserves take in their cells.
Algae
• Green Algae (Phylum Chlorophyta):
• The most plant-like of the algae as they have
the same type of chlorophyll and the same
colour as most land plants.
• Like plants, their cell walls contain cellulose
and store food reserves in the form of starch.
• Found in freshwater, damp terrestrial places
and even live in the fur of sloths!
Algae
• Brown Algae (Phylum Phaeophyta):
• Nearly all multicellular, which are commonly
called seaweeds.
• Cell walls made of cellulose and alginic acid
(similar to pectin, which is used to thicken jams
and jellies).
• Have adaptations to live in rough environments
such as holdfasts that anchor the algae to the
rocky seashore. Their fronds are tough enough
to withstand the pounding of the waves.
Algae
• Red Algae (Phylum Rhodophyta):
• multicellular seaweed found in warmer seawater.
• More delicate and smaller than brown algae.
• Why are they red? Because they contain
pigments that absorb green, violet and blue light
and since these wavelengths penetrate the
furthest in water, they are able to live at deeper
depths.
In Class Work
• Pg 93, Q 1-6
The Shift to Land
• Hypothesis that green algae are the
closest evolutionary relatives of land
plants based on
– Presence of chlorophyll a and b
– Cellulose cell walls
– Store food in form of starch
– Similarities in genetic code
• However there are key
Adaptations to Life on Land
• Since plants live in terrestrial environments,
need protection from drying and system to
transport water and nutrients
• Plants only evolved from aquatic to terrestrial
environments 460 million years ago
– Reproduce using embryos (spores in algae)
– Development of vascular tissue, seeds and flowers
Vascular tissue, leaves and roots
• First land plants were small and simple and did
not have vascular tissue; eventually evolved to
vascular plants
• Vascular tissue allowed evolution of roots
– Allowed anchoring
– Absorb and transport water
– Increased range of plants into drier environments
• Leaves came next
– Increased surface area of plant allowed better
exchange of gases involved in photosynthesis and light
capture
Kingdom Plantae
General Characteristics
• Use photosynthesis to gain energy, therefore
autotrophic.
• Live in all aquatic and terrestrial habitats except
at the poles.
• Are the main source of oxygen for the planet
• The basis for every food chain or food web
Classification of Plantae
• Although there are a vast
variety of plants in the
world, they can all be
placed in one of four main
groups based on vascular
tissue and seeds.
• Each large group
contains several
divisions, which are the
rough equivalent to a
Phylum.
Classification of Plants
• Bryophytes (mosses)
– non-vascular, seedless
• Ferns
– vascular, seedless
• Gymnosperms (conifers)
– vascular, non-enclosed seeds
• Angiosperms (flowering plants)
– vascular, enclosed seeds
1) Non-Vascular Plants (Mosses )
• Three divisions (mosses, hornworts and liverworts).
• No vascular tissue, therefore depend on osmosis and
diffusion to transport nutrients.
• Usually grow in dense mats of low tangled vegetation
that can hold water like a sponge, allowing them to
survive cold or dry periods.
• Have no roots, instead have root-like rhizomes.
• Sexual reproduction.
Non-vascular Plants
Mosses (Bryophytes)
• Very successful and widespread, thrive in such diverse
habitats as bogs, tundra, on bare exposed rocks, and in deep
shade.
• Twice as many species of mosses as there are mammals!
Liverworts (Hepatophytes)
• Grow flat, low to the ground and are rarely more than 30 cells
thick.
• 80% are leafy and live in tropical forests and in humid
climates.
• Many small chloroplasts per cell.
Hornworts (Anthocerophytes)
• Broad, flat and are commonly blue-green in colour.
• One large chloroplast per cell
2) Seedless Vascular Plants (Ferns
and their relatives)
• came about 300 million years ago
• developed the vascular tissue that allowed them
to grow tall
Seedless Vascular Plants
Whisk Ferns (Psilotophytes)
• Look like small green whisk brooms
• No leaves or roots
• Short rhizomes, which are horizontal, underground
stems.
• Produce spores.
Club Mosses (Lycopodophytes)
• Small evergreen-looking plants that grow in dense
mats in moist temperate or tropical forests.
• Not related to true mosses!
• Have true roots and stems.
Horsetails (Sphenophytes)
•
Once included tree-sized members, but now just smaller plants
(1 m).
•
Often found in damp areas or along roadsides.
•
Can be used to scour pots.
•
Have silica in their cells, which accounts for the roughness.
•
Can be made into a shampoo to combat head lice.
Ferns (Pteridophytes)
•
Dominated the forests during the Carboniferous period (315280 mya).
•
Most familiar and successful of the seedless vascular plants.
•
Have roots, stems, a waxy epidermis that reduces water loss
by evaporation and stomata in their leaves for gas exchange.
•
Ferns produce millions or even billions of spores in their
lifetime.
•
Have fronds, which are seed leaves that grow up from
rhizomes.
3) Gymnosperms (Conifers)
• disperse by means of seeds
• reproduce sexually without needing water
• have seeds that are exposed on the surface of cone scales
• gymnosperm means ‘naked seed’
• includes cone-bearing trees: pines, firs, spruce, yew, cedars,
redwood and many other large trees.
• Also includes the cycadophytes, gnetophytes and
ginkgophytes.
3) Gymnosperms
Conifers
•
Form vast forests in the colder regions of the world
•
As well as reproducing without water, they have bark to
prevent water loss.
•
The pyramidal shape of many conifers helps snow and ice
slide off the tree reducing branch breakings.
•
The needle like leaves have a thick, waxy cuticle and sunken
stomata, which reduce the rate of evaporation.
•
These are evergreens, which are continually losing and
replacing needles all year round.
Gnetophyta
•
Very rare, found in southern Africa
Gymnosperms
Cycadophyta
• 100 species in the tropics, once dominated the earth.
• Short, palm-like trees with scaly trunks.
Ginkgophyta
• The only living species is Ginko biloba, which was
common during the Jurassic period (200 mya).
•
Cultivated in Asian temples for hundreds of years,
which helped protect against extinction.
4) Angiosperms (Flowering Plants)
• Plants that protect their seeds within the body of a fruit
are called angiosperms or flowering plants.
• Appeared on earth more than 150 mya.
• Include vines, grasses, shrubs, trees and water plants.
• Grow everywhere on land from tundra to tropics.
• Divided into monocots (1 seed leaf) and dicots (2 seed
leaves). Seed leaves (cotyledon nourish the growing
embryo
• Sexual reproduction by pollination. Use wind, water,
animals, bats, birds and insects as pollen carriers.
Monocots vs. Dicots
In Class Work
• Pg 101, Q 13-18
Kingdom Fungi
Learning Goals
Introduction to Fungi
• Mushrooms, toadstools,
mildews, yeasts and
moulds are all members
of this kingdom.
• Some unicellular fungi,
but most are multicellular.
• Look similar to a plant but
also have much in
common with animals.
Fungi Morphology
• Multicellular species have ‘bodies’
made up of hyphae, a network of
fine filaments
• You can’t see these as clearly in
mushrooms because they are so
densely packed together in a tight
mass
• The mushroom part you see is only
one part of the complex fungus.
•
• The majority of the organism is
contained underground in the form
of a loose branching network of
hyphae called mycelium
Fungal Nutrition
• Parasitic
– Cordyceps invade ants body
• Predatory
– Soil fungi have mycelia for trapping small worms
• Mutualistic
– Mycelia of Mycorrhiza found on plant roots increase
surface area allowing more nutrients to enter plants. The
fungus gets sugar from plant
• Saprobial
– Saphrobes feed on dead matter. Recycle nutrients in
ecosystems
Feeding
• The majority are
saprotrophs, which
means they break down
decaying matter and play
a big role in the recycling
of nutrients.
• As hyphae grow across a
food source, they release
digestive enzymes that
break down large organic
molecules into smaller
organic molecules
Feeding
• It is extracellular digestion
because it happens
outside the body
• The more extensive the
mycelium the more space
for absorbing nutrients
Parasitic Fungi
• Some fungi are parasites and can cause
diseases such as athlete’s foot and ringworm.
They are specialized and produce hyphae
called haustoria which penetrates host’s cells
without killing them (Dutch Elm Disease)
• Cordyceps invades and kills ants by
absorbing the ant’s internal cavity through its
growing hyphae
• http://www.youtube.com/watch?v=vgkL8PulPdE
Fungal Reproduction
• Most fungi have both asexual and sexual
methods of reproduction
• The simplest asexual way is fragmentation, in
which pieces of the hyphae are broken off and
grow into new mycelia. This happens if
something breaks the mycelium, like a
gardener, for instance…
Fungal Reproduction
• The majority of fungi live on land and therefore
produce haploid spores, which are windblown
reproductive cells that help the fungi disperse to
new locations.
• The spores are produced in great number to help
increase the chances of dispersal and survival.
• A puffball can produce as many as one trillion
spores!
Classifying Fungi
• Original ancestors of fungi are not known. They
may have evolved separately from more than
one origin.
• Five subgroups…
1) Imperfect Fungi (Deuteromycotes)
• Only reproduce
asexually
• Do not have a sexual
phase of reproduction,
hence the term
‘imperfect fungi’.
• Develop mycelium from
spores called conidia
1) Imperfect Fungi (Deuteromycotes)
• Very diverse group
containing very important
members such as: the
mould, penicillin, which
grows on mouldy fruit and is
an important antibiotic,
cyclosporin is obtained from
a fungus that lives in the soil,
it is a drug that is used after
transplant to help suppress
the rejection of the
transplanted organ.
• Others are used to make soy
sauce and blue cheese.
2) Chytrids
• Unicellular and aquatic
• Can be parasites or live on decaying
matter
• Potato wart
3) Zygospore Fungi (Zygomycotes)
• Multicelluar and terrestrial
• Include bread moulds and other saprotrophs
• Reproduce asexually, but under certain conditions will
undergo sexual reproduction
• During this sexual reproduction, they produce zygospores
which give this group their name.
4) Sac Fungi (Ascomycotes)
• Largest group of fungi. Include powdery mildews on leaves,
single-celled yeasts and truffles
• Most are saprotrophs that break down the hard to digest
materials in wood and bone
• Other species are parasites of plants producing leaf curl,
chestnut blight
• Identified by small fingerlike sacs called asci (ascus), which
they develop during sexual reproduction
• Usually reproduce asexually
• Yeasts use budding to reproduce (p 108).
5) Club Fungi (Basidiomycotes)
• Include mushrooms that
grow on lawns, bracket
fungi on dead tree trunks
and the puffballs found
on woodland floors.
• Release spores called
basidiospores from
hyphae called basadia
5) Club Fungi (Basidiomycotes)
• Some club fungi are
parasites of plants. They are
called ‘smuts’ or ‘rusts’ and
can cause lots of damage on
crop plants.
• The largest part of the club
fungi is a vast sprawling
network of hyphae that
spread underground.
• Complex reproductive cycle.
Usually reproduce sexually.
Lichen
• Composite organism because they form an
organism of two different species
• Fungus and a photosynthetic organism (green
algae or cyanobacteria)
• Can live in harsh or nutrient-poor conditions
• Food source for many animals
In Class Work
• Pg 107, Q 19-24