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Liverworts and Mosses
• 16,000 bryophytes species show some adaptations for life on land
• They have root-like structures for anchoring called rhizoids
• These structures can also bring water up but they have to rely on
diffusion to distribute the water throughout the plant
• Because of this most bryophytes are less than 2 cm. tall
Enclosed Reproductive Structures
• These structures represent adaptation to terrestrial life
• they prevent the gametes from drying out
• The archaegonia house the eggs while antheridia house the sperm
• some species have separate male and female plants
• Some plants have both parts
• In all species, the sperm has to swim to the egg
Liverwort
archaegonia
Sperm cells have to swim up the
stalks, through a film of water to
fertilize the eggs
Tracheophytes
• Vascular plants
• Two types of adaptations allowed some plants to become taller
• Structures that provide support
• vessels that conduct water and nutrients
Seedless Vascular Plants
• These plants reached tree-like heights and dominated the landscape
from 360 mya to 286 mya
• Modern versions are the club mosses, ferns and horsetails
• The ancient ancestors are coal today
CLUB MOSS
Lycopodium
HORSETAILS
Equisetum
FERNS
Lycopodium and Equisetum
• There are only 15 species of horsetails
• commonly called “scouring rushes”
• they are abrasive due to deposits of silica in their outer layer of cells
• club mosses are commonly called “ground pine”
• all are only a few centimeters tall
Ferns
• There are 12000 species of ferns
• In the tropics, there are “tree ferns”
• Ferns are the only seedless plant with broad leaves
• This gives them an advantage and may account for their relative
success
Seed Plants
• Have dominated the land for the past 250 million years
• this was made possible by the development of pollen and seeds
• In seed plants both the female and male gametophytes are greatly
reduced in size
• the female gametophyte is a small group of cells that produce eggs
• the pollen is the male gametophyte
The Seed
• It is analogous to the egg in birds and reptiles
• The seed consists of an embryonic plant, a food supply for the
embryo, and a protective coat
• The embryo can lay dormant until the conditions are right for growth
• Some seeds possess elaborate adaptations for dispersal
Gymnosperms
• Non-flowering seed plants
• There are three divisions
• coniferophyta
• ginkgophyta
• cycadophyta
Conifers
• There are 500 species of conifers
• They include pines, firs, spruce, hemlocks and cypresses
• Most abundant in cold latitudes and high elevations
• Their advantages are retaining their leaves all year as to
photosynthesize when other plants are dormant
continued
• And, their needle-like leaves have small surface area so evaporation is
minimized
• Third, they have a substance in their sap that acts like an anti-freeze.
It also gives them the pine scent.
Ginkgo
• Were once widespread during the Jurassic period
• Today, there is only one species, Ginkgo biloba
• Ginkgos have separate male and female plants
• they are very resistant to pollution and the males are used for
landscaping
Cycads
• Kind of look like ferns but aren’t
• There are about 160 species today
• They live in the tropics and sub-tropical areas
• Grow slowly and live for a loooooooong time
• Some specimens are estimated to be 5000 years old
• Seeds used to be food but they contain a neurotoxin so….not so much
anymore
Angiosperms
• Flowering plants
• Incredibly diverse with 352,000 species
• They can be a few millimeters wide (duckweed) to 328 feet tall
(eucalyptus tree)
• Have been around for more than 100 million years
Three Major Adaptations
• Flowers
• fruit
• broad leaves
• Broad leaves are appealing to herbivores so angiosperms have
evolved lots of defense mechanisms
• thorns, spikes, resins, toxins
• Humans have used many of the poisons as medicine
Two Types of Angiosperms
Dicotyledons (dicots)
Monocotyledons (monocots)
Monocots
• About 65,000 species
• Includes grasses, grains, corn, irises, lilies, and
palms
• Have one cotyledon or “seed leaf”
• Vascular bundles (xylem and phloem) scattered
throughout stem
• Xylem conducts water up from roots
• Phloem conducts sugars from photosynthesis
Dicots
• About 170,000 species
• Includes most trees, shrubs, and herbs
• Have two cotyledons
• Vascular bundles arranged in rings in stem