Plants

Characteristics of Plants

Eukaryotic

Cell walls that contain cellulose

Autotrophic

Plants can carry out photosynthesis, converting

sunlight energy into chemical energy

light

light

Roles of Plants Producers

Foundation of ecosystems due to their ability to photosynthesize

Produce chemical energy that can be taken in by other organisms for use

Medicinal Uses

Discovery of chemical compounds that can be used as natural remedies

Nutrient Cycles

Cycling of nutrients in an ecosystem (e.g. carbon, nitrogen, oxygen, etc.)

Pollution clean-up

Able to clean up soil through bioremediation where plants absorb pollution such as metals from the environment

Evolution of plants

The ancestor of modern-day plants were aquatic organisms similar to green algae.

Adaptations that allowed plants to live on land include the following:

Development of lignin

Ability to stand upright and grow tall for sunlight

Development of vascular tissue

Ability to transport nutrients, waste, and water

Development of seeds

Formation of an embryo

Strategies to reduce water loss

Strategies to disperse reproductive structures without water currents

Plant Alternation of Generations

Alternation of generations – Life cycle that

alternates between diploid and haploid forms

Most plants have both a diploid phase and a

haploid phase in their life cycle

Diploid generation

Sporophyte that produces haploid spores

Haploid generation

Gametophyte that produces haploid gametes

Concept Check

What key characteristics do plants share?

Describe four adaptations plants developed that

allowed them to grow on land.

A plant life cycle shows alternation of generations.

Describe the alternation of generations of a plant.

List the differences between the sporophyte and

gametophyte plant generations.

Major Groups of Plants

Green Algae – Modern Relatives of Plant Ancestors

Green Algae – Modern Relatives of

Plant Ancestors

Ancestry – Closest living relative of plant ancestors

Habitat – shallow fresh water, e.g. edges of ponds

and lakes

Life cycle - do not undergo an alternation of

generations

Structure – Different from photosynthetic plant-like

protists because they have cell walls and

photosynthetic pigments that are identical to plants

Mosses and Relatives – Seedless Non-vascular plants

Mosses and Relatives – Seedless

Non-vascular plants

Group known as bryophytes which can be classified

as a type of non-vascular plant

Ancestry – Modern relatives of first group to diverge

from the ancestral algae ancestors with the

development of lignin

Habitat – moist environments

Life cycle – Spend most of their life cycle in the

gametophyte generation. Sperm are flagellated

and swim through water to reach eggs.

Structure – Low growing due to the lack of rigid

support structures. No stems or seeds.

Ferns and Relatives – Seedless Vascular Plants

Ferns and Relatives – Seedless

Vascular Plants

Ancestry – Modern relatives of first plants

demonstrating vascularization which is the

formation of tubes to carry fluid throughout an

organism

Habitat – moist environments

Life cycle – Spend most of their life cycle in the

sporophyte generation. Sperm are flagellated and

swim through water to reach eggs.

Structure – Have vascular tissues connecting the

roots to the shoots. This helps transport water and

dissolved nutrients throughout the plant.

Gymnosperms -Seed Plants

Gymnosperms -

Seed Plants

Ancestry – Modern relative of first plants that have

seeds, which are plant embryos.

Habitat – diverse land habitats

Life cycle – highly developed sporophyte

generation and a gametophyte generation that

produces male gametophytes in the form of pollen

grains (can travel through dry environments)

Structure – Have a gametophyte generation that

grows off the sporophyte generation (e.g. cones on

a pine tree). Seeds are not enclosed (‘naked’).

Angiosperms –Flowering Plants

Angiosperms –

Flowering Plants

Ancestry – Modern relative of first plants that have enclosed seed. Also known as flowering plants. Evolution coincides with the rise of mammals.

Habitat – diverse land habitats

Life cycle – highly developed sporophyte generation and a gametophyte generation that produces male gametophytes in the form of pollen grains (can travel through dry environments)

Structure – Gametophytes of angiosperms develop within the flowers of sporophytes. Flowers attract insects and animals for reproduction and seed dispersal. Fruits, ripened ovaries of flowers, are also produced which aid in dispersal.

Plant Kingdom

Highly organized

tissues

Vascular tissues

Dispersed by seeds

Seeds enclosed

Angiosperms (flowering

plants)

Seeds not enclosed

Gymnosperms

(conifers)

Dispersed by spores

Ferns

No vascular tissues

Bryophytes

(mosses)

No highly organized

tissues

Green algae

Concept Check

What are the major group (or phyla) of plants?

What are characteristics of these phyla?

What advantages does vascularization provide to

plants?

What advantage does the seed provide?

What is the most effective reproductive and seed-

dispersal structure in the plant kingdom?