introduction to plant life interest grabber plants make the world go round life as we know it today...

Introduction to Plant Life

Interest Grabber

Plants Make the World Go Round

Life as we know it today could not exist without plants.Plants provide us with many essential items other than food.

1. With your partner, list five items you usedaily that are byproducts of plants.

2. With your partner, list three items that plants must get from animals—either directly or indirectly.

3. Using your answers to questions 1 and 2, construct a diagram that illustrates the interdependence of plants and animals.

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Section Outline

Introduction to PlantsA. What Is a Plant?

B. The Plant Life Cycle

C. What Plants Need to Survive

1. Sunlight

2. Water and Minerals

3. Gas Exchange

4. Movement of Water and Nutrients

D. Early Plants

1. Origins in the Water

2. The First Plants

E. Overview of the Plant Kingdom

Section 22-1

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What is a plant?

Dominant group of organisms on land (based on biomass)

Characteristics:

Size ranges from 2mm to 100 m tall.

Most are photosynthetic

Some are parasitic


HaploidDiploid MEIOSIS

Spores(N)

Sporophyte Plant (2N)

Gametophyte Plant (N)

FERTILIZATION

Sperm(N)

Eggs(N)

Section 22-1Generalized Plant Life Cycle

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KEY CONCEPT Plant life began in the water and became adapted to land.


Land plants evolved from green algae. • Plants and green algae have many common traits.

– both are photosynthetic eukaryotes – both have the same types of chlorophyll – both use starch as a storage product – both have cell walls with cellulose


• Genetic analysis points to the common ancestor of all plants.

– extinct green algae species in class Charophyceae– modern charophyceans common in lakes and ponds


• Important plant characteristics likely originated in charophyceans.– multicellular body allowing for specialization of

cells and tissues

– cell division that allows for chemical communication between cells

– reproduction involving sperm swimming to egg


– Ancestral charophyceans lived in areas of shallow water.

• True plants evolved through natural selection.

– Those that could survive longer dry periods were favored.

– First true plants probably grew at edges of water.– True plants have embryos that develop while attached

to female parent.


• True plants evolved through natural selection.


Plants have adaptations for life on land

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• Land plants are a clade, defined by a set of derived characters

– Alternation of haploid and diploid generations– Walled spores produced in sporangia– Male and female gametangia– Multicellular, dependent sporophyte embryos



• Life on land offered new opportunities– Unlimited sunlight

– Abundant CO2

– Initially, few pathogens or herbivores



• Challenges of terrestrial life– Maintaining moisture within cells– Obtaining resources from soil and air– Supporting body in air– Reproducing and dispersing offspring without

water


• Challenges of living on land have selected for certain plant adaptations.

• A cuticle allows plants to retain moisture.– waxy, waterproof layer

– holds moisture in


• Stomata are tiny holes in the cuticle.

stoma

– can open and close– allow air to move in and out


• A vascular system allows resources to move to different parts of the plant.

sugars

water and mineral nutrients

– collection of specialized tissues– brings water and mineral nutrients up from roots

– disperses sugars from the leaves – allows plants to grow higher off the ground



Plant diversity reflects the evolutionary history of the plant kingdom

• Four key adaptations for life on land distinguish the main lineages of the plant kingdom

– Dependent embryos (characteristic of all plants)– Lignified vascular tissues– Seeds– Flowers


• Lignin allows plants to grow upright.

– hardens cell walls of some vascular tissues– provides stiffness to stems

plant cells

lignin


• Pollen grains allow for reproduction without free-standing water.

– pollen grains contain a cell that divides to form sperm

– pollen can be carried by wind or animals to female structures



• In all plants, the zygote develops into an embryo while attached to and nourished by the parent plant

• Plants are embryophytes, with multicellular, dependent embryos


• A seed is a storage device for a plant embryo. – seed coats protect

embryos from drying wind and sunlight

– embryo develops when environment is favorable


Plants evolve with other organisms in their environment. • Plants and other organisms can share a mutualistic

relationship. – a mutualism is an interaction in which two species

benefit– plant roots and certain fungi and bacteria – flowering plants and their animal pollinators


• Plants have adaptations that prevent animals from eating them.

– defensive chemicals

– spines and thorns


Spores

Flagellatedsperm

Stem Leaf

Seed

Pollen

Leaf

FernStomata; roots anchor plants,absorb water; lignified cellwalls; vascular tissue;fertilization requires moisture

Roots

Stem

Roots

Pine treeStomata; roots anchor plants, absorb water; lignified cell walls; vascular tissue;fertilization does not require moisture

MossStomata only on sporophytes; primitive roots anchor plants,no lignin; no vascular tissue;fertilization requires moisture

Spores

Flagellatedsperm

Leaf

Stem

Roots

Flagellatedsperm

Vasculartissue

Key

Holdfast(anchors alga)

AlgaWater supportsalga. Whole algaperforms photo-synthesis;absorbs water,CO2, andminerals fromwater.


Flagellatedsperm

Stem

Leaf

FernStomata; roots anchor plants,absorb water; lignified cellwalls; vascular tissue;fertilization requires moisture

Roots

MossStomata only on sporophytes; primitive roots anchor plants,no lignin; no vascular tissue;fertilization requires moisture

Spores

Flagellatedsperm

Leaf

Stem

Roots

Flagellatedsperm

Vasculartissue

Key

Holdfast(anchors alga)

AlgaWater supportsalga. Whole algaperforms photo-synthesis;absorbs water,CO2, andminerals fromwater.

Spores


Leaf

Seed

Pollen

Stem

Roots

Pine treeStomata; roots anchor plants, absorb water; lignified cell walls; vascular tissue;fertilization does not require moisture

Vasculartissue

Key


Cone-bearing plants760 species

Ferns andtheir relatives11,000 species

Mosses andtheir relatives15,600 species

Floweringplants235,000 species

Section 22-1

Figure 22-7 The Diversity of Plants

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introduction to plant life interest grabber plants make the world go round life as we know it today...

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