Plants

Kingdom Plantae• Plants evolved about 500 million years ago

from simple green algae that lived in the ocean.

• All plants are autotrophic and some, like the famous Venus fly-trap, can also be heterotrophic.

Plant CellsLike animal cells, plant cells contain a nucleus and organelles, but they have two distinguishing features:– Cell wall (made of

cellulose - provides rigid structural support)

– Chloroplast (conducts photosynthesis)

Biodiversity & Plant Diversity• Biodiversity refers to the # of different species and

the # of individuals within each species• Currently over 350,000 species of plants, including:

– Mosses– Ferns – Conifers (gymnosperms) – Flowering plants (angiosperms)

• Most plants live on land and can withstand a wide variety of climates. Cacti live in arid, dry areas whereas mosses need to be in moist environments to survive.

• High biodiversity in rainforests (warm & wet) and low biodiversity in extreme environments such as arctic and deserts (extreme temp, windy, dry).

• Loss of a plant species can reduce biodiversity (perhaps it is the only source of food for certain animal species or insects, etc).

World Plant Biodiversity

Classifying Plants

• Plants are classified based on:– the presence or absence of

vascular tissue– Production of seeds (seed or

non-seed)

• Vascular tissue can be compared to arteries and veins:– a network of specialized cells

that allows plants to transport water, minerals and sugar throughout the plant

• What would you expect a non-vascular plant, without vessels to transport nutrients and water, to look like?

VASCULAR PLANTS

NON-VASCULAR PLANTS (Bryophytes)

DEFINITION

EXAMPLES

STEMS, ROOTS, AND LEAVES?

UPTAKE OF WATER AND NUTRIENTS

OTHER

Network of specialized cells to provide transport of water and nutrients throughout plant

No network of specialized cells for transport of water and nutrients throughout plant

Flowering plants (angiosperms), conifers (gymnosperms), ferns

Mosses & liverworts/hornworts

Osmosis, diffusion and active transport

Lack true leaves and roots

Grow low and close to the ground; must live in moist environments or near presence of water

Yes to all

Through stems, leaves and roots, and their cells

Can grow tall, can live in variety of environments

Classifying Plants: Seed or Non-Seed

• Plants may or may not have the ability to produce seeds as part of their reproductive life cycle – All plants, however, can reproduce sexually and

asexually = alternation of generations

• Seeds are specialized reproductive structures that contain a plant embryo

• Non-Seed Plants: Mosses & Ferns

• Seed Plants: Flowering Plants (Angiosperms) & Conifers (Gymnosperms)

Seed Plants• Important to humans because they provide us

with food • Why it is advantageous to be a seed plant:

– Can sexually reproduce without free water– Can sexually reproduce with another individual far

away– Plant embryo surrounded by a protective coat– Seeds can be dormant till environmental

conditions are “just right”– Seeds can be carried by wind, water or by

animals to other parts of the ecosystem (or even a new ecosystem)

Seed Plants• Can be grouped into:

– Angiosperms (flowering plants). They are grouped further into:

• Monocots• Dicots

– Gymnosperms (conifers, etc)

More later on!

ANGIOSPERMS GYMNOSPERMS

TYPE OF PLANTS

LEAVES & ROOTS

SEEDS

ECOSYSTEMS & PRACTICAL USES

Woody plants – wood-producing trees & shrubs, conifers including evergreens (pines, firs, cedars, etc)

Herbaceous plants – lack woody tissues; flowering plants (some trees can be in this group)

Conifers have needles for leaves (small surface area, thick waxy coat = prevents water loss. Roots are shallow & spread out = anchors the tree in areas where soil is sparse.

“Naked seed” = no coatConifers have male and female cones. Pollen grains inside male cone are carried by wind to female cone, where egg is fertilized

Boreal Forest and Temperate Rain Forests (hardier than angiosperms)Wood, paper/pulp, varnishes, fuel come from gymnosperms

Seed has coat. Male stamen and female pistil (or carpel) on same flower. Pollen from male moves down flower to female part to fertilize the egg. Embryo forms within seed.

Diverse ecosystemsFood crops and products, perfumes, medicine

Leaves are usually flat to maximize photosynthesis. Leaves have pores.True roots to hold down plant & take in nutrients.

Angiosperms

1. Male anther produces pollen grains (sperm)

2. Pollen grains from one flower is carried by wind or organisms (eg. Bird, insect) to another flower. Pollen grains travel down pollen tube to the ovary (female egg)

3. Sperm fertilizes the egg to form a zygote (embryo) within a seed

4. Seed can develop further within a fruit (ovary wall)

5. Seed can be released with or without the fruit and will develop into a new sporophyte plant

Male (bottom) and Female (top) Pine Cones

Gymnosperms 1. Male pollen cones produce microspores, which develop into pollen grains (sperm)

2. Pollen grains from a male cone is carried to the female seed cone by wind or an organism.

3. Sperm fertilizes the egg to form a zygote (embryo) within a seed

4. Zygote forms into a seed cone (female)

5. Seed (with wing) can be released and forms into a new sporophyte plant that will grow more.