What is a Plant? with Plant Diversity

Chapter 21 & 22

What is a plant? Multicellular

eukaryote Produce their own

food through photosynthesis

Have thick cell walls made of cellulose

Stems & leaves of most have a waxy waterproof coating called a cuticle

Origins of Plants Scientists hypothesize

that all plants probably evolved from filamentous green algae that lived in the ancient oceans

Some of the evidence for their relationship can be found in modern members of both groups

Comparing Plants to Algae1. Green algae and plants

have cell walls that contain cellulose

2. Both groups have the same types of chlorophyll used in photosynthesis and store food in the form of starch.

The 1st plants The first evidence of

plants in the fossil record began to appear over 440 million years ago

These early plants were simple in structure and did not have leaves.

They were probably instrumental in turning bare rock into rich soil

Adaptations of Plants1. Preventing water loss:

Most fruits, leaves, and stems are covered with a protective, waxy layer called the cuticle

The waxy cuticle creates a barrier that helps prevent the water in the plant’s tissues from evaporating into the atmosphere

Adaptations of Plants2. Carrying out

photosynthesis: The leaf, is a plant organ that grows from a stem and usually is where photosynthesis occurs

Each plant species has unique leaves or leaflike structures

Adaptations of Plants3. Putting down roots:

Plants can take in water and nutrients from the soil with their roots

In most plants, a root is a plant organ that absorbs water and minerals usually from the soil

Roots anchor a plant usually in the ground & function as storage.

Adaptations of Plants4. Transporting

materials: Water moves from the roots of a tree to its leaves, and the sugars produced in the leaves move to the roots through the stem

A stem is a plant organ that provides support for growth.

Transporting Materials It contains tissues for transporting food, water,

and other materials from one part of the plant to another

Stems also can serve as organs for food storage In green stems, some cells contain chlorophyll

and can carry out photosynthesis.

Xylem & Pholem

Xylem & Pholem

Transporting materialsTransporting materials

Phloem Xylem

Cambium

Xylem transports water and dissolved substances other than sugar throughout the plant.

Phloem transports dissolved sugar throughout the plant.

Cambium produces xylem and phloem as the plant grows.

Nonvascular Plants Nonvascular plants do not have the

conducting tissues xylem and phloem Examples: mosses, liverworts & hornworts

Nonvascular Plants

Moss

No true roots, stems, or leaves, must live near water or moist environment

Vascular Plants Vascular plants have tubes and vessels to

transport water and nutrients (Xylem & Phloem) Grass, trees, flowers, ferns

Vascular plants can live farther away from water than nonvascular plants.

Vascular Plant are divided into: Seed Plants-flowers, pines, trees, grasses

subdivided into:

angiosperms-flowering plants

gymnosperms-cone bearing plants Seedless plants-ferns

Vascular Plants

Vascular & Nonvascular Plants

Embryo

Seed Coat

Food Supply

A seed is a plant organ that contains an embryo, along with a food supply, and is covered by a protective coat.

It also protects the embryo from drying out and also can aid in its dispersal

Reproductive Strategies (1)

Reproductive Strategies (2) In non-seeded plants

(mosses & ferns) the sperm requires a film of water on the gametophytes plant to reach the egg

Reproductive Strategies (3)

In seed plants, which include all conifers and flowering plants, sperm reach the egg without using a film of water

This difference is one reason why non-seed plants require wetter habitats than most seed plants

Spores In non-seed vascular plants

such as ferns, spores have hard outer coverings

Spores are released directly into the environment where they can grow into haploid gametophyte plants

These plants produce male and female gametes

Following fertilization, the sporophyte plant develops and grows on the gametophyte plant.

Seeds In seed plants, such as

conifers and flowering plants, spores develop inside the sporophyte and become the gametophytes.

The gameotophytes consist of only a few cells

Male and female gametes are produced by these gametophytes

After fertilization, a new sporophyte develops within a seed. The seed eventually is released and the new sporophyte plant grows.

Non seeded Plants

Non-seed Plants Non-seed plants include

vascular or nonvascular organisms.

•There are 7 divisions of Non-seeded plants. ThesePlants produce hard-walledReproductive cells calledSpores

•Non-seed plants are either vascularOr non-vascular

Hepaticophyta: Liverworts

Small plants commonly called liverworts because the flattened body of the plant and it resembles the lobes of an animals liver

They grow in moist environments

They use osmosis & diffusion to transport water

Found from Artic to Antarctic Some found in water, others in

deserts

Most have an oily/shiny surface

2 kinds of liverworts:1. Thallose liverwort:

have broad body that looks like a lobed leaf

The body of a thallose liverwort is called a thallus.

Found growing on damp soil

2 kinds of liverworts:2. Leafy Liverwort: are

creeping plants with 3 rows of thin leaves attached to a stem

Leafy liverworts grow close to the ground and usually are common in tropical jungles and areas with persistent fog

Their stems have flat, thin leaves arranged in three rows—a row along each side of the stem and a row of smaller leaves on the stem’s lower surface

Anthocerophyta: Hornwort Small Plants Sporophytes

resembles the horns of an animal

Nonvascular plant-grows in damp, shady habitats

Relies on osmosis & diffusion to transport nutrients

Hornworts Are the smallest division

of nonvascular plants Currently consisting of

only about 100 species are similar to liverworts

in several respects

Bryophyta: Mosses Nonvascular plants Rely on osmosis and

diffusion to transport materials

Habitats include close to streams, rivers or humid tropical forest

Limited in size (less than 5 cm tall)

Cannot compete with vascular plants

Mosses Mosses: More familiar than

liverworts Small plant w/ leafy

stems Grow in dense carpets

or turfs Mosses have rhizoids,

which help anchor the stem to the soil.

Some have upright stems; others have creeping stems that lie along the ground or hang from steep banks or tree branches

Mosses Some mosses form extensive mats that help retard

erosion on exposed rocky slopes Moses grow in a wide variety of habitats, even in

the arctic during the brief growing season where sufficient moisture is present

A well-known moss is Sphagnum, also known as peat moss. This plant thrives in acidic bogs in northern regions

of the world. It is harvested for use as fuel and is a commonly used soil additive

Psilophyta: Wisk Ferns Consist of thin, green

stems. Are unique vascular

plants because they have neither roots nor leaves

Small scales that are flat, rigid, overlapping structures cover each stem.

•The two known genera of psilophytes are tropical or subtropical, only 1 found in U.S.

Lycophyta: Club Mosses Vascular plants adapted

primarily to moist environments

Have stems, roots, and leaves Their leaves, although very

small, contain vascular tissue Ancestors grew as tall as 30 m

and formed a large part of the vegetation of Paleozoic forests

The plants of these ancient forests have become part of the coal that is now used by people for fuel.

Club Moss

The club moss, Lycopodium, is commonly called ground pine because it is evergreen and resembles a miniature pine tree

Some species of ground pine have been collected for decorative uses in such numbers that the plants have become endangered

Arthrophyta: Horsetails Vascular plants They have hollow,

jointed stems surrounded by whorls of scalelike leaves

The cells covering the stems contain large deposits of silica

About 15 species of arthrophytes exist today

Horsetail Early horsetails were tree-sized members of the

forest community. Today’s arthrophytes are much smaller than their ancestors

There are only about 15 species in existence, all of the genus Equisetum

These plants also are called scouring rushes because they contain silica, an abrasive substance

Most horsetails are found in marshes, in shallow ponds, on stream banks, and other areas with damp soil

Pterophyta: Ferns

The most well-known and diverse group of non-seed vascular plants.

They have leaves called fronds that vary in length from 1 cm to 500 cm

The large size of fronds is one difference between pterophytes and other groups of seedless vascular plants

Although ferns are found nearly everywhere, most grow in the tropics

Ferns According to fossil records, ferns—division

Pterophyta—first appeared nearly 375 million years ago

Ancient ferns grew tall and treelike and formed vast forests

In most ferns, the main stem is underground. This thick, underground stem is called a rhizome.

Fronds

Root

Rhizome

Fern Structures

The leaves of a fern are called fronds and grow upward from the rhizome.

The fronds are often divided into leaflets called pinnae, which are attached to a central rachis.

The branched veins in ferns transport water and food to and from all the cells.

Fern spores are produced in structures called sporangia

Fern Structures

Sorus Clusters of sporangia

form a structure called a sorus (plural, sori). Sori are usually found on the underside of fronds but in some ferns, spores are borne on modified fronds

Seeded Plants

Cycadophyta: Cycads Were abundant during

the Mesozoic Era. Today, there are about

100 species of cycads They are palmlike trees

with scaly trunks and can be short or more than 20 m in height

Cycads produce male and female cones on separate trees

Cones Cones are woody strobili

scaly structures that support male or female reproductive structures

Seeds are produced in female cones.

Male cones produce clouds of pollen

Diversity of Cone Bearing Trees

Trees that bear cones are called gymnosperms

Characteristics:

produce seeds in cones (pines, firs, cedars)

needle-like leaves

Male cones: produce pollen

Female cones: contain seeds

Adaptations in Coniferophyta The reproductive structures of most conifers are

produced in cones.

Male cones

Female cone

Wing

Pollen grain

Spores

Pollen sac

Ovule

Two seeds

Wing

Evergreen confiers: trees that are green year round & photosynthesize when conditions are right

Deciduous trees: lose their leaves each fall to conserve water through winter conditions

Gnetophyta: Gnetophytes There are three genera of gnetophytes (NEE toh

fites) and each has distinct characteristics

1. Gnetum (Nee tum) includes about 30 species of tropical trees and climbing vines

Gnetophyta: Gnetophytes There are about 35

Ephedra (eh FEH dra) species that grow as shrubby plants in desert and arid regions

Gnetophyta: Gnetophytes Welwitschia (wel

WITCH ee uh) has only one species, which is found in the deserts of southwest Africa

Its leaves grow from the base of a short stem that resembles a large, shallow cap

Ginkogophyta: Ginko biloba This division has only one

living species, Ginkgo biloba, a distinctive tree with small, fan-shaped leaves

All ginkgoes are cultivated trees, and they are not known to exist in the wild

Ginkos Ginkgoes (GING kohs) have male and female

reproductive structures on separate trees. The seeds produced on female trees have an

unpleasant smell, so ginkgoes planted in city parks are usually male trees

Ginkgoes are hardy and resistant to insects and to air pollution

Coniferophyta: Cone-Bearing Trees

These are the conifers (KAH nuh furz), cone-bearing trees such as pine, fir, cypress, and redwood

vascular seed plants that produce seeds in cones

Species of conifers can be identified by the characteristics of their cones or leaves that are needlelike or scaly.

Bristlecone pines, the oldest known living trees in the world, are members of this plant division.

Another type of conifer, the Pacific yew, is a source of cancer-fighting drugs.

Bristlecone Pine

Anthophyta: The Flowering Plants

Commonly called the flowering plants, are the largest, most diverse group of seed plants living on Earth

There are approximately 250 000 species

Unlike conifers, anthophytes produce flowers from which fruits develop

Diversity of flowering plants Flowering plants, also

called angiosperms, produce seeds enclosed within a fruit.

A fruit includes the ripened ovary of a flower.

Anthophyta

Monocotyledons (mah nuh kah tul EE dunz) include grasses, orchids, lilies, and palms

Dicotyledons (di kah tul EE dunz).

A fruit usually contains one or more seeds. Division has 2 classes

Monocot Characteristics

Dicot Characteristics

An embryo is an early stage of development of an organism

Embryos of seed plants include one or more cotyledons

Cotyledons usually store or absorb food for the developing embryo.

Seed coat

Cotyledon

Cotyledons

Cotyledons

Parts of the Flower Male: Stamen

Parts: Anther & Filament Female: Pistol

Parts: Stigma, Style, Ovaries, & Ovule

female

male

Parts of an Angiosperm

Life span of anthophyta1. Annual plants live for only a year or less. They

sprout from seeds, grow, reproduce, and die in a single growing season.

Annuals form drought-resistant seeds that survive the winter.

Life span of anthophyta2. Biennial plants have life spans that last two years

-1st year: grow many leaves and develop a strong root system

-Over the winter, the aboveground portion of the plant dies back, but the roots remain alive

-2nd year: food stored in the root is used to produce new shoots that produce flowers and seeds.

Life span of anthophyta3. Perennials live for several years, producing flowers

and seeds periodically—usually once each year

They survive harsh conditions by dropping their leaves or dying back to soil level, while their woody stems or underground storage organs remain intact and dormant