Chapter 22 Plant Diversity

22–1 Introduction to Plants

Objectives Explain what a plant is Describe what plants need to survive Describe how plants first evolved

What Is a Plant? Plants are members of the kingdom Plantae Plants are multicellular eukaryotes that have cell walls made of cellulose. They develop from multicellular embryos and carry out photosynthesis using the green pigments chlorophyll a and b

The Plant Life Cycle Plants have life cycles that are characterized by alternation of generations the two generations are the haploid (N) gametophyte, or gamete-producing plant, and the diploid (2N) sporophyte, or spore-producing plant.

What Plants Need to Survive Sunlight Water and Minerals Gas Exchange Movement of water and nutrients

Early Plants The first plants evolved from an organism much like the multicellular green algae living today.

The First Plants  The first true plants were still dependent on water to complete their life cycles, similar to today’s mosses in that they were simple in structure and grew close to the ground.

From these plant pioneers, several major groups of plants evolved.

Mosses

Ferns

Cone Bearing Plant

Flowering plant

Overview of the Plant Kingdom Botanists divide the plant kingdom into four groups based on three important features: Water conducting tissues Seeds Flowers

22 – 2 Bryophytes a.k.a (Non-vascular plants)

Objectives Describe the adaptations of Bryophytes

bryophytes Type of early plant with no vascular tissue that draw water in their cells by osmosis.

Moss

Liverwort

Hornwort

During at least one stage of their life cycle, bryophytes produce sperm that must swim through water to reach eggs of other individuals. Therefore, they must live in places where there is rainfall or dew for at least part of the year

Asexual Reproductive Part Sexual Reproductive/ Photosynthetic Part

22–3 Seedless Vascular Plants

Objectives Explain how vascular tissue is important to ferns and their relatives Describe the three phyla of spore-bearing plants Identify the stages in the cycle of ferns

In just a few million years, plants grew to a whole new scale on the landscape. Q: What caused this increase in size? A: Vascular Tissue

Vascular tissue A type of tissue that is specialized to conduct water and nutrients through the body of the plant

Evolution of Vascular Tissue Both forms of vascular tissue—xylem and phloem—can move fluids throughout the plant body, even against the force of gravity.

Xylem Carry water upwards from the roots to every part of the plant

Phloem Transports nutrients and carbohydrates produced by photosynthesis from the leaves down to the roots

Vascular plants also evolved the ability to produce lignin, a substance that makes cell walls rigid. The presence of lignin allows vascular plants to grow upright and tall

Ferns and Their Relatives Seedless vascular plants include club mosses, horsetails, and ferns. Like other vascular plants, ferns and their relatives have true roots, leaves, and stems.

Roots Absorb water and minerals

Leaves Collect light for photosynthesis

Veins Made of xylem and phloem

Stems Used for support, connect roots and leaves, carry water between them

Club Mosses 

Horsetails

Ferns Underground Stem

22 – 4 Seed Plants

Objectives Describe the reproductive adaptations of seed plants Describe the evolution of seed plants Identify the four groups of gymnosperms

Over millions of years, plants with a single trait—the ability to form seeds—became the most dominant group of photosynthetic organisms on land. Seed plants are divided into two groups:

Gymnosperms Cone plants Bear their seeds directly on the surfaces of cones Ex.) conifers, pines, spruces, cycads, ancient ginkgoes and gnetophytes

Angiosperms Flowering plants Bear their seeds within a layer of tissue that protects the seed Ex.) grasses, flowering trees shrubs, wild flowers

Reproduction Free From Water Unlike mosses and ferns, however, seed plants do not require water for fertilization of gametes. Q: Why was this an advantage? A: They could live further away from water Adaptations that allow seed plants to reproduce without water include flowers or cones, the transfer of sperm by pollination, and the protection of embryos in seeds.

Cones and Flowers

Cones Seed bearing structures of gymnosperms

Flowers Seed bearing structures of angiosperms

Pollen

Pollen grain Contains the male gamete

Pollination The transfer of pollen from the male gametophyte to the female gametophyte

Seeds

seed An embryo of a plant that is encased in a protective covering and surrounded by a food supply

embryo Early development stage of a sporophyte plant The seed’s food supply provides nutrients to the embryo as it grows

Seed Coat Surrounds and protects the embryo and keeps the contents of the seed from drying out Can be specialized for dispersal

Evolution of Seed Plants Over a period of millions of years, continents became much drier, making it harder for seedless plants to survive and reproduce. For that reason, many moss and fern species became extinct. They were replaced by seed plants with adaptations that equipped them to deal with drier conditions.

Gymnosperms—Cone Bearers The most ancient surviving seed plants are the gymnosperms.   Gymnosperms include:

Gnetophytes

Cycads

Ginkgos

Conifers

22–5 Angiosperms - Flowering Plants

Objectives Identify the characteristics of angiosperms Explain what monocots and dicots are Describe the three different life spans of angiosperms

Flowering plants originated on land and quickly came to dominate Earth’s plant life. The vast majority of living plant species reproduce with flowers.

Flowers and Fruits Angiosperms have unique reproductive organs known as flowers. Q: Why are flowers evolutionary adaptations? A: they attract animals that pollinate them

Flowers contain ovaries, which surround and protect the seeds After pollination, the ovary develops into a fruit, which protects the seed and aids in its dispersal.

Fruit Ripened ovary, thick wall of tissue that surrounds the seed

Diversity of Angiosperms The angiosperms are an incredibly diverse group. Not surprisingly, there are many different ways of categorizing these plants.

Monocots and Dicots Monocots and dicots are named for the number of seed leaves, or cotyledons, in the plant embryo. Monocots have one seed leaf, and dicots have two seed leafs

Woody and Herbaceous Plants Woody plants – Have woody stems Ex.) trees, shrubs, vines

Herbaceous Plants Plant stems that are smooth and nonwoody Ex.) dandelions, petunias, and sunflowers

Annuals, Biennials, and Perennials

Annuals Angiosperms that complete a life cycle within one growing season

Biennials Angiosperms that complete their life cycle in two years In the first year, biennials germinate and grow roots, stems, leaves During their second year, biennials grow new stems and leaves and then produce flowers and seeds

Perennials Flowering plants that live for more than two years