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 PlantaeKingdom Plantae

General CharacteristicsGeneral 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 PlantaeClassification 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 PlantsClassification 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 )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 PlantsNon-vascular PlantsMosses (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 2) Seedless Vascular Plants (Ferns and their relatives) and their relatives)

• came about 300 million years ago• developed the vascular tissue that allowed them

to grow tall

Seedless Vascular PlantsSeedless 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 (315-

280 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)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) Gymnosperms3) GymnospermsConifers• 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

GymnospermsGymnosperms

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)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 FungiKingdom Fungi

Learning Goals

Introduction to FungiIntroduction 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 MorphologyFungi 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

FeedingFeeding

• 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

FeedingFeeding

• It is extracellular digestion because it happens outside the body

• The more extensive the mycelium the more space for absorbing nutrients

Parasitic FungiParasitic 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 ReproductionFungal 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 ReproductionFungal 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 FungiClassifying Fungi

• Original ancestors of fungi are not known. They may have evolved separately from more than one origin.

• Five subgroups…

1) Imperfect Fungi (Deuteromycotes)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)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)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)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)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)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