Plant Classification AP Biology Unit 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

Land Plants What are the advantages of being a land plant? –High concentrations of CO 2 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