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21 Cards in this Set

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  • Back

Objectives of this Unit

* Distinguish between evolutionary and ecological approaches to study of vegetation

* understand basic classification units that are used in describing plants and vegetation

* describe how plants respond to biotic and abiotic environmental factors

appreciate the fact that plant communities are dynamic , ever changing entities

* understand how various human activities can affect the distribution and characteristics of vegetation

Two approaches can be employed in trying to understand the plant cover of the earth

1. Evolutionary / historical approach

2. Environmental relationship and ecology

Evolutionary approach

attempts to decipher how different plants and plant types "taxa" have evolved in the past and how their distribution patterns have developed in response to previous climatic and geologic conditions

Relationship of plant communities

Ecological plant geography - emphasis on plant communities as part of ecosystems.

3 types of Cryptogams

1. Thallophytes

2. Bryophytes

3. Pterdophytes

1. Thallophytes

algae or fungi, simple body for not differentiated into leaf, stem or roots

2. Bryophytes

Mosses and liverworts

3. Pteridophytes

ferns, clubmosses, horsetails.

Main classes of Phanerogams

1. Gymnosperms

2. Angiosperms

1. Gymnosperms

Seeds and ovules are not protected and are usually born in cones.

2. Angiosperms

Flowering plants, in which ovules are contained in protective carpels and the seeds in a fruit


complex of interacting abiotic conditions influencing the plantcommunity in a particular location

Climatic factors

include temperature, light, moisture, and humidity, radiation and insolation

climatic factors are important

t for a wide rangeof physiological processes such as germination, seed setting, and leaf growth.Both the microclimate (the “climate near the ground”) and the regionalclimate are of great influence.

Topographic (geomorphic) factors

include altitude, slope, and aspect.Topography most often has an indirect effect on plants and vegetation,influencing soil drainage, stability, or microclimate, which then directlyinfluence plants.

Soil (edaphic) factors

include the nutrient content, physical structure, texture,and moisture content of the soils in which plants grow.

Biotic factors

Biotic factors include the influence of animals on plants (for example, throughgrazing or trampling) but also include the competition of plants betweenthemselves for limited resources

Plants and vegetation are sometimes classed asmicrothermal

if they are adapted to low temperatures

, mesothermal

if adapted tomoderate temperatures


megathermal if adapted to high temperatures.

cardinal points

All plant growth takes place within two critical temperatures, or cardinal points. At temperatures above the upper cardinal point, plant growth ceases. Below thelower cardinal point, temperatures are too low for growth, and somewherebetween these two extremes is the optimum temperature for growth