Plant Classification

AP BiologyUnit 5

Plant Diversity• All plants are

thought to have evolved from ancestral green algae

• Within the plant kingdom, there are many different types

Algae– NOT a plant!

• Algae is a multicellular protist

• Green algae has many characteristics in common with plants, but also some distinguishing characteristics

Land versus Water Plants

• What are the advantages of being a water plant? – More access to water– More support (from the

surrounding water) – Water helps disperse gametes

Image taken without permission from http://www.blupete.com/Nature/PictureFlowers/WaterLilyPink2.jpg

Land Plants

• What are the advantages of being a land plant?– High concentrations of CO2 in

air (compared to water)– More access to sunlight– Initially: less competition for

resources, fewer predators

Nonvascular vs. Vascular

• Land plants can be classified as vascular or nonvascular

• Nonvascular (Nontracheophyte) = no xylem or phloem

• Vascular (Tracheophyte) = has a xylem and phloem

Nonvascular Plants

• No internal transport system

• Smaller in size

• Grow in large, dense mats

• Have rhizoids = structures that help anchor the plant into the ground

• Ex. Mosses, Liverworts, Hornworts

Question…

• Why can’t nonvascular plants be very tall?

• Without xylem and phloem, they are unable to transport water and nutrients efficiently throughout the plant can’t grow as tall since they can’t get the water up very high.

Vascular Plants

• Vascular tissue used to transport water, minerals, sugar, hormones

• Have the potential to grow taller

• Can be further divided into seed and nonseed plants

• Ex. Ferns, conifers, flowering plants

Vascular Plants- Nonseed plants

• Pterophytes (Ferns)– Have a xylem and phloem– Do not have seeds to protect plant embryo

Vascular Plants- Seed plants

• Gymnosperms (Conifers)– Seed is not protected by fruit– Has cones

• Angiosperms (Flowering Plants)– Seed is further protected by a

fruit– Has flowers