Chapter 3

January 16th

Light• Sunlight controls the distribution of plants

• Amount of sunlight depends on latitude

• With respect to light, plants classified into 2 categories:– Heliophytes

• Obligate

• Facultative

– Sciophytes• Obligate

• Facultative

Morphological Adaptations to Light

Succulents

Banana plant (Moorea)

Sargassum

Sunflower

Temperature• Transpiration allows plants to be cooler than or

warmer than the surrounding air temperature• The rate of photosynthesis is dependent upon

temperature

Adaptations to heat

• Features that decrease leaf temperature:

• Reflective coatings

• Small hairs

• Leaves oriented vertically

• Heliotrophs

• High transpiration rates

• Leaf loss

• Dimorphism

Temperature

• Cold-blooded animals are pokiliotherms• Warm-blooded animals are homeotherms• Allen’s Rule – short extremities relative to

body mass decreases heat loss• Bergmann’s Rule – warm-blooded individuals

from cooler climates tend to have larger bodies and smaller surface-to-volume rations, and individuals of the same species from warmer climates

Allen’s Rule/ Bergmann’s Rule

Allen’s Rule/ Bergmann’s Rule

Moisture

• Required by plants for photosynthesis and temperature control

• Xerophytes

• Mesophytes

• Hydrophytes

• Transpiration

• Evapotranspiration

Moisture

• Three categories of adaptations to dry conditions:– Water stress escapees

– Water stress avoiders

– Water stress toleraters

• Two fundamentals for describing geographic distributions of a species: range and density

• Geographic range – entire area where a species can be found regardless of whether it is common or rare

• Density – Difference in abundance of species within its range

• Carrying capacity – the number of individuals an environment can support per meter or hectare

Carrying Capacity

Ordination Analysis

Figure 3.13

Environmental Gradients for Physiological Functioning and Density

• Zone of optimum –

• Zone of stress –

• Zone of intolerance –

• Zone of tolerance -

• Niche – the function of a species in the environment

• Habitat – explicit spatial environment where a species can be found

• Generalists – species that can tolerate a wide range of environmental conditions

• Specialists – species that have narrow environmental tolerances

Limiting Factors

Limiting Factors