Kingdom PlantaeKingdom Plantae

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 differences

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 rootsAllowed anchoringAbsorb 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

General CharacteristicsGeneral CharacteristicsUse photosynthesis to gain energy, therefore

autotrophic.

Live in all aquatic and terrestrial habitats except at the poles.

Through photosynthesis plants take in carbon dioxide and provide oxygen for the environment.

Three main parts of the plant are root, stem and leaves.

General characteristics cont.

Roots - penetrate the soil to anchor the plant and reach sources of water

Leaves - provide a greater surface area for photosynthesis

Stem - supply rigid tissues that raise and support the leaves

Vascular tissue acts like a circulatory system and transports water, nutrients, and dissolved minerals to all parts of the plant

A seed is a structure made up of an embryo, stored food and tough waterproof coat

Life cycle consists of two generations which alternate between a haploid gametophyte and diploid sporophyte stage.

Classification of PlantaeClassification of Plantae

Although there are a vast variety of plants (over 300,000 known species) 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 PlantsBryophytes (mosses)

non-vascular, seedless

Ferns vascular, seedless

Gymnosperms (conifers) vascular, non-enclosed seeds

Angiosperms (flowering plants) vascular, enclosed seeds

1) 1) Non-Vascular Plants (MossesNon-Vascular Plants (Mosses and their relatives)and their relatives) Three divisions (mosses, hornworts and liverworts).

No vascular tissue, so 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 which are small root like structures

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! Sporophytes do not contain chlorophyll

Liverworts (Hepatophytes) Grow flat, low to the ground and are rarely more than 30

cells thick. 80% are leafygametophytes that resemble mosses. Live in

tropical forests and in humid climates. 20% have gametophystes with flattened, lobed bodies

called thalli that resemble the lobes of animal’s livers. Many small chloroplasts per cell.

Non-Vascular Plants cont.

Hornworts (Anthocerophytes)

Broad, flat

Usually blue-green in colour.

Sporophyt looks like mini-green cattle horns

One large chloroplast per cell

2) Seedless Vascular Plants (Ferns 2) Seedless Vascular Plants (Ferns and their relatives) and their relatives) Originated about 300 million years agodeveloped vascular tissue that allowed them

to grow tallSporophyte (diploid) generation becomes

dominant stage in life cycleGametophytes are short-lived and require

moisture to carry out sexual reproduction

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 and different than other 2 groups.

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 Largest group of gymnosperms. Form vast forests in the

colder regions of the world

Covering of bark helps protect the stem and reduce water loss.

Have a pyramidal shape and flexible branches to help snow and ice slide off the tree reducing branch breakings.

needle like leaves have a thick, waxy cuticle and sunken stomata, which reduce the rate of evaporation.

Most conifers are evergreens, so they continually lose and replace their needles all year round.

Better able to grow in nutrient poor soils because they do not need to grow a complete set of leaves all at once.

Gymnosperms cont.Gymnosperms cont.

Gnetophyta Very rare, found in southern Africa May live 100 years. Produces two broad leaves that it

keeps its entire life.

Cycadophyta Short, palm-like trees with scaly trunks. Mainly exists

in the tropics. Common trees when dinosaurs roamed the earth.

Ginkgophyta Distinctive lobed leaves. 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 4) Angiosperms (Flowering Plants)Plants) Plants that protect their seeds within the body of a fruit

are called angiosperms or flowering plants.

Include vines, grasses, shrubs, trees and water plants.

Grow almost everywhere on land from tundra to tropics.

Flower contains sexual reproductive structures, use wind, water, animals, bats, birds and insects as pollen carriers.

Divided into monocots (1 seed leaf) and dicots (2 seed leaves). Seed leaves (cotyledon nourish the growing embryo Appeared on earth more than 150 mya. More than ¾ of all species of living plants!

Monocots vs. Dicots

http://www.ted.com/talks/jonathan_drori_the_beautiful_tricks_of_flowers.html