Chapter 50. An Introduction to Ecology and the Biosphere

Transcription

1 Chapter 50 An Introduction to Ecology and the Biosphere

2 50.2: Interactions between organisms and the environment limit the distribution of species Ecologists have long recognized global and regional patterns of distribution of organisms within the biosphere Many naturalists began to identify broad patterns of distribution by naming biogeographic realms

3 LE 50-5 Many naturalists identify broad patterns of distribution by naming biogeographic realms Nearctic Palearctic Tropic of Cancer (23.5 N) Oriental Ethiopian Equator (23.5 S) Tropic of Capricorn Neotropical Australian

4 LE 50-6 Biogeography - Provides a good starting point for understanding what limits geographic distribution of species Species absent because Dispersal limits distribution? Yes No Area inaccessible or insufficient time Behavior limits distribution? Yes No Habitat selection Biotic factors (other species) limit distribution? Yes No Predation, parasitism, competition, disease Abiotic factors limit distribution? Chemical factors Water Oxygen Salinity ph Soil nutrients, etc. Physical factors Temperature Light Soil structure Fire Moisture, etc.

5 Dispersal and Distribution Dispersal is movement of individuals away from centers of high population density or from their area of origin Dispersal contributes to global distribution of organisms

6 Natural Range Expansions Natural range expansions show the influence of dispersal on distribution

7 Species Transplants Species transplants include organisms that are intentionally or accidentally relocated from their original distribution Species transplants can disrupt the communities or ecosystems to which they have been introduced

8 Behavior and Habitat Selection Some organisms - do not occupy all of their potential range Species distribution - may be limited by habitat selection behavior

9 Biotic Factors Biotic factors that affect the distribution of organisms may include: Interactions with other species Predation Competition

10 Seaweed cover (%) A specific case of an herbivore limiting distribution of a food species EXPERIMENT W. J. Fletcher tested the effects of two algae-eating animals, sea urchins and limpets, on seaweed abundance near Sydney, Australia. In areas adjacent to a control site, either the urchins, the limpets, or both were removed. RESULTS Fletcher observed a large difference in seaweed growth between areas with and without sea urchins August 1982 Limpet Sea urchin February 1983 Both limpets and urchins removed Only urchins removed Only limpets removed Control (both urchins and limpets present) August 1983 February 1984 Removing both limpets and urchins or removing only urchins increased seaweed cover dramatically. Almost no seaweed grew in areas where both urchins and limpets were present, or where only limpets were removed. Figure 50.8 CONCLUSION Removing both limpets and urchins resulted in the greatest increase of seaweed cover, indicating that both species have some influence on seaweed distribution. But since removing only urchins greatly increased seaweed growth while removing only limpets had little effect, Fletcher concluded that sea urchins have a much greater effect than limpets in limiting seaweed distribution.

11 Abiotic Factors Abiotic factors affecting distribution of organisms: Temperature Water Sunlight Wind Rocks and soil

12 Temperature Environmental temperature is an important factor in distribution of organisms because of its effects on biological processes

13 Water Water availability in habitats is another important factor in species distribution

14 Sunlight Light intensity and quality affects photosynthesis Light is also important to development and behavior of organisms sensitive to photoperiod

15 Wind Wind amplifies effects of temperature by increasing heat loss from evaporation and convection Wind can change morphology of plants

16 Rocks and Soil Many characteristics of soil limit distribution of plants and thus the animals that feed upon them: Physical structure ph Mineral composition

17 Climate Four major abiotic components of climate: temperature, water, sunlight, and wind Climate is the prevailing weather in an area Macroclimate consists of patterns on the global, regional, and local level Microclimate consists of very fine patterns, such as those encountered by the community of organisms underneath a fallen log

18 Global Climate Patterns Global climate patterns are determined largely by solar energy and the planet s movement in space Lower angle of in coming sunlight Direct sunlight at equinoxes Lower angle of in coming sunlight Sunlight intensity plays a major part in determining the Earth s climate patterns Seasonal variations of light and temperature increase steadily toward the poles Atmosphere

19 LE 50-10b June solstice: Northern Hemisphere tilts toward sun; summer begins in Northern Hemisphere; winter begins in Southern Hemisphere. 60 N 30 N 0 (equator) 30 S March equinox: Equator faces sun directly; neither pole tilts toward sun; all regions on Earth experience 12 hours of daylight and 12 hours of darkness. Constant tilt of 23.5 September equinox: Equator faces sun directly; neither pole tilts toward sun; all regions on Earth experience 12 hours of daylight and 12 hours of darkness. December solstice: Northern Hemisphere tilts away from sun; winter begins in Northern Hemisphere; summer begins in Southern Hemisphere.

20 Global air circulation and wind patterns play major roles in determining climate patterns

21 LE 50-10d Westerlies Northeast trades Doldrums Southeast trades Westerlies Arctic Circle 60 N 60 S Antarctic Circle 30 N 0 (equator) 30 S

22 Regional, Local, and Seasonal Effects on Climate Various features of the landscape contribute to local variations in climate Trees/no trees Elevation Latitude Seasonal variation also influences climate

23 Bodies of Water Oceans and their currents and large lakes moderate the climate of nearby terrestrial environments

24 Mountains Mountains have a significant effect on The amount of sunlight reaching an area Local temperature Rainfall

25 Seasonality The angle of the sun leads to many seasonal changes in local environments Lakes are sensitive to seasonal temperature change and experience seasonal turnover

26 Lake depth (m) Lake depth (m) LE Lake depth (m) Lake depth (m) Lakes O 2 (mg/l) Winter Spring O 2 (mg/l) O 2 concentration C 0 4 C High (>8 mg/l) Medium (4 8 mg/l) Low (<4 mg/l) O 2 (mg/l) O 2 (mg/l) Autumn 4 C Thermocline 4 C Summer Are sensitive to seasonal temperature change - Experience seasonal turnover

27 Microclimate Microclimate is determined by fine-scale differences in abiotic factors

28 Long-Term Climate Change One way to predict future global climate change is to study previous changes

29 ANY QUESTIONS?