Chapter 22 Introduction to Plants

Characteristics of Plants

Classified as members of the Kingdom Plantae. Plants are Eukaryotes that have cell walls containing cellulose and carry out photosynthesis using chlorophyll a and b located in chloroplasts. Most plants are autotrophs, a few are parasites or saprobes.

What plants need

Sunlight: Plants use energy from sunlight to carry out photosynthesis so they have adaptations on their leaves to maximize light absorption.
Gas Exchange: plants need oxygen for cellular respiration and they need carbon dioxide for photosynthesis. They re

Origins in the water

Ancestors of today's plants were water dwelling organisms similar to today's green algae. most of these were unicellular.

Green algae

Now considered part of plant kingdom because it has cell walls and photosynthetic pigments identical to those of plants. Also, it has reproductive cycles similar to plants and their genomes suggest that they are closely related to plants.

The first land plants

First land plants lacked leaves and roots which made it hard to obtain water. Fossils suggest first land plants were dependent on water to complete their life cycle. Over time, the demands of life on land favored the evolution of plants more resistant to

Major Groups of Plants

Green Algae, Mosses, Ferns, Cone-bearing plants, and Flowering Plants. These Five major plant groups are based on four important features: embryo formation, specialized water-conducting tissues, seeds, and flowers.

The plant life cycle

The life cycle of land plants has two alternating phases, a diploid (2n) and a haploid (N) phase. This sexual life cycle sets plants apart from other living organisms.
** A sporophyte produces haploid spores through meiosis. These spores grow into multice

Alternation of generations

The shift between haploid and diploid phases in the plant life cycle.

Sporophyte (spore producing plant)

the multicellular diploid (2N) phase of the plant life cycle

Gametophyte (gamete producing plant)

The multicellular haploid (N) phase. Haploid (N) carries one set of chromosomes, while diploid (2N) have two sets of chromosomes.

Trends in plant Evolution

Over time there has been a reduction in size of the gametophyte and an increase in the size of the sporophyte. This size difference is seen especially in seed plants which have an even smaller gametophyte contained within sporophyte tissues.

Green Algae

Green algae were the first plants on the earth. Evident in the fossil record from the Cambrian period. Green algae are mostly aquatic. They are found in fresh and salt water, and in some moist areas on land. Most are single cells or branching filaments so

Green Algae Life Cycle

Many have life cycles that switch back and forth between haploid and diploid phases, but they may not alter every generation. EX: The single celled green alga Chlamydomonas. It can switch from asexual reproduction to sexual reproduction as environmental c

Green Algae Mulitcellularity

Many green algae from colonies. Spirogrya forms long, threadlike colonies called filaments. Volvox colonies are more complex than the spirogyra, cells are arranged to form hollow spheres. Volvox cells are connected to one another by strands of cytoplasm,


Group of plants that have specialized reproductive organs enclosed by other, non reproductive cell. Bryophytes are small because they lack vascular tissue. = MOSSES. They have a higher degree of cell specialization than do the green algae.


bryophytes. short, soft plant. thin waxy coating that make it possible for them to resist drying, and thin filaments knows as rhizoids that anchor them to the skid. The RHIZOIDS absorb water and minerals from the soil. Mosses do not have vascular tissue.

vascular tissue

specialized tissue in land plants that contains tubes hardened with lignin that enable them to carry water. Bryophytes do not make lignin and do not contain true vascular tissue.

Life cycle of Mosses (Bryophytes)

byrophytes display alternation of generations. Gametophyte is the dominant, recognizable stage of the life cycle. The gametophyte is the stage that caries out most of the plants photosynthesis. The sporophyte is dependent on the gametophyte for its supply

Bryophyte Gametophyte

as the gametophyte grows, it forms rhizoids that from into the ground and shoots that grow into the air. These shoots turn into the familiar green moss plants. Gametes are formed in reprodutive structures at the tips of gametophytes. Some bryophyte specie


where eggs are produced in the gametophyte.


where sperm are produced in the gametophyte.

Bryophyte Sporophyte

The zygote produced in the gametophyte phase marks the beginning of the sporophyte stage of the life cycle. It develops into a multicellular embryo growing within the body of the gametophyte. It grows out of the gametophyte and develops a long stalk endin


The spore capsule that grows out of the bryophyte gametophyte. Inside the capsule, haploid spores are produced by meiosis. The capsule ripens and opens, and haploid spores are scattered to the wind to start the cycle again. P. 642

Vascular Plants

Fossil evidence shows plants developed vascular tissue to carry water and nutrients and were thus able to grow high above the ground. The vascular tissues in these plants - xylem and phloem, make it possible for vascular plants to move fluids through thei


Also known as vascular plants, after a specialized type of water-conducting cell they contain. Include all seed bearing plants, but vascular tissue is also found in plants that do not produce seeds.


Water conducting cells in vascular plants. They are hollow tubelike cells with thick cell walls strengthened by lignin. One of the great evolutionary innovations of the plant kingdom. They are found in xylem where they are connected end to end like a seri


where the tracheids are found. Xylem is a tissue that carries water upward from the roots to every part of a plant.


transports solutions of nutrients and carbohydrates produced by photosynthesis. the main cells of phloem are long and specialized to move fluids throughout the plant body.

Seedless vascular plants.

these vascular plants include club mosses, horesetails, and ferns. Ferns are the most numerous seedless vascular plants. They have true vascular tissues, strong roots, creeping or underground stakes called rhizomes, and large leaves called fronds.

Vascular Plant Life cycle

Ferns and other vascular plants have a life cycle in which the diploid sporophyte is the dominant stage. Haploid spores grow into thin, heart-shaped haploid gametophytes (N). The gametophyte grows independently of the sporophyte. Sperm and eggs are produc


a plant embryo and a food supply, encased in a protective covering. It contains a living, diploid (2N), plant that represents the early developmental stage of the sporophyte phase of the plant life cycle.

The first seed plants

Ancestors of seed plants evolved new adaptations that allowed seed plants to reproduce without open water. These adaptations include a reproductive process that takes place in cones or flowers, the transfer of sperm by pollination, and the protection of e

Cones and flowers.

reproductive structures within seed plants where the gametophytes develop. Seed plants are divided into two groups based on which structures they have.

1. gymnosperms

(naked seed) Cone bearing plants. They bear their seeds directly on the scales of the cones. Male cones produce male gametophytes (pollen grains), Female cones produce female gametophytes which are directly on the inside surface of scales (seed cones).

2. angiosperms

Flowering plants. They bear their seeds in flowers inside a layer of tissue that protects the seed. Most flowers produce both male gametophytes (pollen grains) and female gametophytes in each flower. Some species have separate male and female flowers.

Pollen grain

a tiny structure in seed plants containing the entire male gametophyte. Sperm produced by this gametophyte do not swim through water to fertilize eggs, instead they float through the air attaching to people and animals to travel ti the female reproductive


After fertilization, the zygote contained within a seed grows into a tiny plant, the sporophyte embryo.

seed coat

protective coating that surrounds and protects the embryo and keeps the contents of the seed from drying out. seeds can survive tough conditions. The embryo begins to grow when conditions are right. It does this by using nutrients from the stored food sup

Lifecycle of a Gymnosperm

reproduction takes place in cones which are produced but the mature sporophyte plant. Pollen cones, male cones, produce pollen grains. One of the haploid (N) nuclei in the pollen grain will divide later to produce two sperm nuclei. Seed cones, or female c

Gymnosperm Pollination and Fertilization

Conifer lifecycle takes 2 years to complete. Cycle begins in spring as male cones release tons of pollen grains that are carried away by the wind where some reach female cones. There, pollen grains are caught in a sticky secretion on the scales of the fem

pollen tube

structure in a plant that contains two haploid sperm nuclei. Once the pollen tube reaches the newly formed female gametophyte within the ovule, one sperm nucleus disintegrates, the other fertilizes the egg contained within the female gametophyte. A diploi

Flowers and Fruit

Angiosperms. most abundant organisms in plant kingdom. their origin in the Cretaceous period makes them the most recent of all plant phyla. Angiosperms develop reproductive organs called flowers. Flowers contain ovaries which surround and protect the seed

advantages of flowers

flowers are an evolutionary advantage because they attract animals such as bees, moths or hummingbirds who carry pollen with them as they leave. because these animals travel from flower to flower, pollination is much more efficient than the wind pollinati

advantages of fruits

after pollination, the ovary develops into a fruit. the fruit is a structure containing one or more matured ovaries. The wall of the fruit helps disperse the seeds inside it, carrying them away from the parent plant. seeds from the fruit enter an animals


seed leaves in an angiosperm embryo. This was first used to classify flowering plants.


angiosperm embryos with one seed leaf or cotyledon.


angiosperm embryo with two seed leaves or cotyledons.


ancient fruit" It is the oldest known plant with reproductive organs like those found in modern flowers. It is more ancient than modern day monocots and dicots and cannot be classified as either.

angiosperm classification

scientific classification now places monocots into a single group but places the dicots in a variety of distinct and different categories, so the term dicot is no longer used for classification.

Angiosperm Clades

1. Amborella Clade: oldest branch of angiosperms. Its floral parts have a spiral arrangement.
2. Water Lily Clade: another very old group.
3. Magnoliids: contains a wide range of floral diversity, from species with small plain flowers to the dinner-plate

angiosperm diversity

angiosperms are often grouped according to the number of their seed leaves, the strength and composition of their stems, and the number of growing seasons they live. These categories can overlap.

Monocots and Dicots

angiosperms may be termed monocots or dicots based on the number of seed leaves, or cotyledons, they produce. Monocots and dicots differ in characteristics such as the distribution of vascular tissue in stems, roots and leaves, and the number of petals pe

Monocot characteristics

seeds = single cotyledon
leaves = parallel veins
flowers = floral parts often in multiples of three
stems = vascular bundles scattered throughout stem
roots = fibrous roots

dicot characteristics

seeds = two cotyledons
leaves = branched veins
flowers = floral parts often in multiples of 4 and 5
stems = vascular bundles arranged in a ring
roots = taproot

woody and herbaceous plants

plants can be subdivided into groups based on the characteristics of their stems.
1. woody plants: are made primarily of cells with thick cell walls that support the plant body. Include trees, shrubs, and vines.
2. herbaceous plants: stems are smooth and

comparing plants by Life Span

1. annuals: grow from seed to maturity, flower, produce seeds, and die in just one growing season. EX: tomatoes, wheat.
2. Biennials: year 1: sprout and grow very short stems and sometimes leaves. Year 2: grow new stems and leaves, flower, produce seeds,