Chapter 12

Introduction to Plants

Section 1: Objectives

Identify 4 characteristics that all plants share.

Describe the 4 main groups of plants.

Explain the origin of plants.

Plant Characteristics

One plant may seem different than another, but all plants have certain things in common.– Plants come in a variety of shapes and sizes.

All plants have the following in common:– Photosynthesis– Cuticles– Cell walls

Plant Characteristics

All plant cells contain chlorophyll (green pigment).

Chlorophyll is found in chloroplasts. Plants use energy from sunlight to make food

from carbon dioxide and water. This process is called photosynthesis. This makes all plants producers.

Plant Characteristics

Most plants live on dry land and need sunlight to survive.

But why don’t plants dry out? Plants are protected by a cuticle. A cuticle is a waxy layer that coats the

surfaces of plants. This keeps the plant from drying out.

Plant Characteristics

How do plants stay upright? They have no skeleton or muscles for

support. They have a rigid cell wall instead. Carbohydrates and proteins form a hard

material inside the cell wall. Cell walls support and protect the plant cell.

Plant Cell Diagram

Plant Characteristics

Plants have 2 stages in their life cycle:

– Sporophyte stage: plants make spores In suitable environments, the spores of these plants

grow into new plants.

– Gametophyte stage: plant produces sex cells These cells cannot grow into new plants. Instead the cells grow into spores and the cycle repeats.

Plant Characteristics

Plants can be divided into 2 main groups:– Nonvascular plants: lack roots, stems, and leaves

Example: mosses

– Vascular plants: has roots, stems, or leaves Example: Tomato plants

These are the 2 main groups that make up Kingdom Plantae.

Plant Characteristics

Vascular plants are divided into 3 groups:– Seedless plants– Gymnosperms– Angiosperms

Non-flowering seedless plants are called gymnosperms.

Flowering seedless plants are called angiosperms.

Plant Groups Chart

Plant Characteristics

What other organisms do plants share a common ancestor with?– What is a common ancestor?

Because plants and algae share many similarities, scientists believe that they share a common ancestor.

Section 2: Objectives

List 3 nonvascular plants and 3 seedless vascular plants.

Explain how seedless plants are important to the environment.

Describe the relationship between seedless vascular plants and coal.

Nonvascular Plants

These types of plants don’t have vascular tissue. They grow in places that are damp and moist. Each cell of the plant must get water from the

environment. Remember, these plants don’t have roots, stems,

or leaves. Examples: mosses, liverworts, & hornworts

Nonvascular Plants

Reasons these plants are important to the environment:– First to grow in a new environment

– Reduce soil erosion

– Food source for some animals

Mosses

Mosses often live together in large groups. They cover soil or rocks with a mat of tiny

green plants. Mosses have leafy stalks and rhizoids. A rhizoid is a root-like structure that holds

the plants in place and helps plants get water and nutrients.

Liverworts and Hornworts

Like mosses, liverworts and hornworts are usually small, nonvascular plants that usually live in damp places.

Nonvascular plants are usually the first plants to live in a new environment, such as newly exposed rock.

When these nonvascular plants die, they form a thin layer of soil.

Seedless Vascular Plants

Examples include ferns, horsetails, and club mosses.

These plants once grew much taller than they actually do today.

In order to adapt to their environments, these plants change their shape and height over time.

Ferns

These grow in many places ranging from cold to warm climates.

Most ferns have a rhizome- an underground stem from which leaves and roots grow.

Ferns still go through the sporophyte and gametophyte stages in their life cycle.

Sporophyte vs. Gametophyte

Importance of Seedless Vascular Plants

These play many roles in the environment:– Help form soil– Prevent soil erosion– Popular houseplants

– The remains of ancient ferns and club mosses form coal.

– Coal is a fossil fuel and is used for energy.

Section 3: Objectives

Describe 3 ways that seed plants differ from seedless plants.

Describe the structure of seeds.

Compare angiosperms and gymnosperms.

Characteristics of Seed Plants

As with seedless plants, the life cycle of seed plants alternates between 2 cycles:

– Sporophyte stage: plant produces spores to be distributed

– Gametophyte stage: plant produces sex cells which mature into spores

Characteristics of Seed Plants

Seed plants produce seeds. Unlike other plants, these plants produce tiny

structures called seeds which help nourish and protect the sporophyte.

Pollen forms within these plants. Pollen: tiny granules that contain the male

gametophyte of seed plants.

Structure of Seeds

A seed forms after fertilization in plants. Seeds have some advantages over seedless

plants:– Have their own food supply– Seeds can be spread by animals– Animals spread seeds more efficiently than

wind spreads spores.

Structure of Seeds

A seed is made up of 3 parts:– Young plant (sporophyte)– Stored food– Seed coat

– The purpose of the seed coat is to surround and protect the sporophyte.

Parts of A Seed

Gymnosperms

These are seed plants that do not have flowers or fruits.

These seeds are usually protected by a cone. Any plant/tree that has cones would be an

example of a gymnosperm. Pine trees are probably the most popular

example.

Gymnosperms

Conifers are probably the most familiar example.

The word conifer comes from 2 words: “cone-bearing.”

Pollination: the transfer of pollen from the male reproductive structure to the female reproductive structure of seed plants

Gymnosperm Life Cycle

Angiosperms

Vascular plants that produce flowers and fruits. Most abundant group of plants. Can be found in almost every ecosystem. Flowers help angiosperms reproduce and some

depend on wind to transfer pollen from plant to plant.

Angiosperms

Divided into 2 classes:– Monocots: have one seed coat

Grasses, onions, palm treesTips of flowers separate in parts of 3Leaves have parallel veins

– Dicots: have 2 seed coatsRoses, cactuses, sunflowersTips of flowers are separated in parts of 4 or 5Leaves have branching veins

Monocots and Dicots

Angiosperms

• Flowering plants provide many land animals with the food they need to survive.

• People use flowering plants in many ways. • Major food crops, such as corn, wheat,

and rice, are flowering plants. • Flowering plants are used to make cloth

fibers, rope, medicines, rubber, perfume oil, and building materials.

Chapter 12 Sec. 3 Pop Quiz

1)List 2 characteristics of seed plants. 2) When does a seed form in plants? 3) List the 3 parts of seeds. 4) What is the difference between

gymnosperms and angiosperms? 5) What does “conifer” mean? 6) List and describe the 2 groups of

angiosperms.

Section 4: Objectives

• List three functions of roots and three functions of stems.

• Describe the structure of a leaf.

• Identify the parts of a flower and their functions.

Transportation In Plants

• There are two types of vascular tissue in plants:

• Xylem is the type of tissue in vascular plants that provides support and conducts water and nutrients from the roots.

• Phloem is the tissue that conducts food in vascular plants.

Transportation In Plants

• Root Functions: The following are the main functions of roots:

• Roots supply plants with water and dissolved minerals.

• Roots hold plants securely in the soil.

• Roots store surplus food made during photosynthesis

Transportation In Plants

• The layers of cells that cover the surface of the roots is called the epidermis.

• After water and minerals are absorbed by the epidermis, they diffuse into the center of the root where the vascular tissue is located.

• A root cap can be found at the end of the root. • The root cap protects the tip and helps the root

continue to grow.

Transportation In Plants

Transportation In Plants

• There are two kinds of root systems— taproot systems and fibrous root systems.

• Taproot systems have a main root, or tap root, that grows downward. Dicots and gymnosperms usually have tap root systems.

• Fibrous systems have several roots that spread out from the base of the stem. Monocots usually have fibrous root systems.

Transportation In Plants

• A stem connects a plant’s roots to its leaves and flowers. A stem also has the following functions:

• Stems support the plant body.

• Stems transport materials between the root system and the shoot system.

• Some stems store materials.

Transportation In Plants

Many plants have stems that are soft, thin, and flexible.

These stems are called herbaceous stems.

A cross section of an herbaceous stem is shown on the next slide.

Herbaceous Plant Stems

Transportation In Plants

Trees and shrubs have rigid stems made of wood and bark.

This wood and bark provides for more support.

These stems are called woody stems.

Woody Plant Stems

Transportation In Plants

The main function of leaves is to make food for the plant.

The structure of leaves, shown on the next slide, is related to their main function— photosynthesis.

Leaf Structure Diagram

Transportation In Plants

• Some leaves have functions other than photosynthesis.

• The leaves of many cactuses are modified as spines. These spines keep animals from eating the cactuses.

• The leaves of sundews are modified to catch insects, which the sundew digests.

Transportation In Plants

• Flowers are adaptations for sexual reproduction.

• Sepals and Petals The modified leaves that make up the outermost ring of flower parts and protect the bud are called sepals.

• Petals are broad, flat, thin leaflike parts of a flower.

Transportation In Plants

• The male reproductive structure of a flower is called a stamen.

• A pistil is the female reproductive structure of a flower.

Plant Structure Diagram