12.1 Plant Origins

How many different plants do you know?

• Grasses• Garden flowers• Trees• Mosses and Ferns• Food plants• Can you think of more?

Characteristics of plants

• All plants are many celled

• All plants are made up of tissue and organs

• All plants have cell walls • Almost all plant cells

contain chlorophyll

• Plants continue to grow throughout it’s entire life.

• Plants differ from algae in that they have adapted to living on land.

Plant Evolution and Classification•Plants evolved from many celled green algae.

Cells of Plants and Green Algae are very similar.•Cell walls made of cellulose•Both store carbohydrates in the form of starch

The first plants•Were small•Lived close to water•Were non-vascular

•Bryophotes such as mosses are living examples

To grow successfully on land:•Plants evolved tube like structures for transporting water throughout the plant.

•These are called vascular plants.

Over time (millions of years)Plants adapted to a wide range of climates

Bryophytes•Non vascular•Mosses are the most common with Over 9500 Species

•Liverworts are also Bryophytes, with over 8000 spceies

Ferns•Ferns are an ancient group of vascular plants•More than 12,000 species are now living.•Most are found in moist, tropical climates

Angiosperms•The first flowering plants, they first appeared about 130 million years ago.•All produce seeds enclosed in fruit or a pod.•More than 235,000 species are known.

Gymnosperms•These are the first plants to evolve seeds.•They produce naked seeds not enclosed in fruit.•Seeds and other adaptations allow these plants to survive in dry places.•More than 700 species are known today.

Club Mosses•These vascular plants are one of the oldest groups.•About 1000 species exist today.

Horsetails•These vascular plants are considered living fossils.•They have changed very little over millions of years.•Only about 15 species are known to survive.

End

Review Worksheet 12.1

• They evolved from many-celled green algae.

• Both have the same pigments, have cell walls of cellulose, and store carbohydrates in the form of starch.

1. What organisms did plants evolve from and what characteristic do they share with their ancestor?

• Nonvascular plants lack tissues for transporting water and are quite small, while vascular plants have vascular tissues for transporting water and can grow to be large.

2. How do nonvascular and vascular plants differ?

• Mosses and liverworts are nonvascular plants.

• Ferns, club mosses, horsetails, gym nosperms, and angiosperms are vascular plants.

3. List some groups of nonvascular and vascular plants.

• Vascular tissues enabled plants to transport water from the roots throughout the plant.

• This allowed plants to live on land.

• Flowers and seeds enable plants to reproduce without water.

4. Name some adaptations of vascular plants.

Describe how these adaptations allow the plants to live in a wide variety of habitats.

Part B Skills Development Infer

Cacti have a number of special adaptations. Complete Table 1 by explaining how the adaptations benefit the plant in its environment

Cactus Structure• Waxy coating

• Thick stems• Photosynthesis that occurs

only at night• Flowering triggered by

ground moisture instead of position of sun

Benefit in Environment• cuts down transpiration

(process by which leaves lose water)

• can store water in them• air is cooler at night, so less

water can evaporate• can make sure there is water

present before flowering so that there will be enough to sustain the bloom