1. An Introduction to Ecology and the Biosphere
Chapter 52

2. What is Ecology?
Ecology is the study of the interactions between organisms and their environments.
In this chapter – we will focus on:
The scope of ecology
Factors affecting the distribution of organisms
Aquatic and terrestrial biomes
The spatial scale of distributions

3. Key Terms to Know Abiotic: nonliving environmental factors
Biotic: living environmental factors
Ecological time: minutes/months/years
Evolutionary time: decades/centuries, etc.
Population: group of individuals of the same species living in a particular area
Community: all organisms of all species that inhabit a particular area
Ecosystem: all biotic and abiotic factors that exist in an area
Biosphere: the global ecosystem – sum of entire planet’s ecosystems

4. What is Biogeography?
Biogeography: the study of past and present distribution of individual species.
Figure 50.4 – continental drift and barriers such as deserts and mountain ranges all contribute to the distinctive floras and faunas found in Earth’s major regions.

5. Flowchart of Factors Limiting Geographic Distribution

6. Factors Affecting the Distribution of Organisms
Species Dispersal
Species transplants
Introduced species
Behavior & Habitat Selection
Biotic Factors
Abiotic Factors

7. (1)Species Dispersal Contributes to the Distribution of Organisms
Dispersal: the distribution of individuals within geographical population boundaries.
Question: Is the distribution of a species limited by dispersal (i.e. by movement of the organisms)?
Answer can be obtained by transplant experiments.
If the transplant is successful, then the organisms just haven’t reached the target area.
If the transplant is not successful, then other factors limit the distribution of the organisms, such as competitors, lack of a food source, etc.
Figure 50.6

8. Problems with Introduced Species
Humans have moved species around the globe!
Can be deliberate or accidental – but BOTH can be BAD!
Example: African Honey Bee (pg. 1097)
Example: Zebra Mussel (pg. 1097)
Why do invaders succeed?
New habitat with no natural predators, often unlimited food supply – potential for rapid population growth.
What’s the harm of the invasion?
out compete native species – disrupt food webs/chains, change ecosystems, kill native species, difficult to control (Kudzu)…the list goes on and on!!!

9. The Tens Rule
Not all introduced species thrive in their new environment – many fail to colonize.
The Tens Rule makes the statistical prediction that an average of one out of ten introduced species become established
And…one out of ten established species become common enough to become pests.

10. (2) Behavior & Habitat Selection Contribute to the Distribution of Organisms
Organisms may not occupy all potentially suitable habitats.  Why?
Evolution doesn’t lead to perfect organisms.
Evolution is an ongoing process. Environments change, but it takes a while for organisms to respond.

11. Biotic Factors Affect the Distribution of Organisms
Organisms that are required for potential community members to colonize may be lacking:
Pollinators, prey, predators that limit competition, etc.

12. Predator-Removal Experiments
Figure 50.9 – Researchers test effects of 2 herbivores (sea urchins & limpets) on the abundance of seaweeds.
Both present (red) – no algal cover.
Predator-removal demonstrates that sea urchins are main herbivores limiting distribution of the seaweeds.

13. (3) Abiotic Factors Affect the Distribution of Organisms
Temperature
Especially for ectotherms
Water
All living things need water for survival (some more than others)
Sunlight
Light intensity limits plant growth!
Wind
Increases heat loss & water loss
Rocks & Soil

14. Major Ecosystems (Biomes) in N. America
Figure – The areas plotted here encompass the range of annual mean temperature and precipitation occurring in the biomes.

15. Temperature & Water are the Major Climatic Factors Determining the Distribution of Organisms
Climate & Biomes:
Climate – prevailing weather conditions at a locality.
Microclimate – climate locally varying on a small scale (i.e. on a forest floor or under a rock).

16. Seasonal Turnover
Ponds & lakes are sensitive to seasonal temperature changes
During summer & winter, many lakes in temperate regions are thermally stratified (layered vertically according to temperature).
Such lakes undergo biannual mixing of their waters as a result of changing water temp. profiles (called turnover).
Turnover brings oxygenated water from surface of lakes to bottom and nutrient rich water from bottom of lake to top
These events are essential for survival and growth of organisms at all levels within the ecosystem!

17. Figure 50.15 – Lake Stratification & Seasonal Turnover

18. Aquatic Biomes Cover About 75% of Earth’s Surface!
Wetlands
Lakes
Rivers, streams
Intertidal zones
Oceanic pelagic biome
Coral reefs
Benthos

19. Distribution of Major Aquatic Biomes

20. Vertical Stratification of Aquatic Biomes
Photic Zone – upper zone; light sufficient for photosynthesis
Aphotic zone – lower zone; little light penetrates
Water temperature also stratified
Colder water is deeper
Oceans (some lakes) have thermocline (narrow layer that separates the two types of water)
Benthic zone – bottom of all aquatic biomes – sand and inorganic sediments
Organisms that live here are called benthos
Benthos survive on detritus

21. Freshwater Biomes Standing bodies (lakes, ponds)
Moving bodies (rivers, streams)
Littoral Zone – regions occupied by floating and rooted plants; shallow water close to shoreline
Limnetic zone – open waters away from shore; occupied by phytoplankton, zooplankton, fish, etc.
Profundal zone – aphotic zone where detritus accumulates
Lakes classified according to production of organic matter
Oligotrophic lakes – deep and nutrient-poor, sparse phytoplankton; clearer water
Eutrophic lakes – shallower, nutrient rich, productive phytoplankton; murky waters result
Mesotrophic – inbetween

22. Oligotrophic Lake: Nutrient poor, water is clear, oxygen rich; little productivity by algae, relatively deep with little surface area.

23. Eutrophic lake: nutrient rich, lots of algal productivity so it’s oxygen poor at times, water is murkier  often a result of input of agricultural fertilizers

24. Rivers and Streams: Organisms need adaptations so that they are not swept away by moving water; heavily affected by man changing the course of flow (E.g. dams and channel-straightening) and by using rivers to dispose of waste.

25. Wetlands: includes marshes, bogs, swamps, seasonal ponds
Wetlands: includes marshes, bogs, swamps, seasonal ponds. Among richest biomes with respect to biodiversity and productivity. Very few now exist as they are thought of often as wastelands. Favor growth of water plants and also rich in invertebrates and birds.

26. Estuary: Place where freshwater stream or river merges with the ocean
Estuary: Place where freshwater stream or river merges with the ocean. Highly productive biome; important for fisheries and feeding places for water fowl. Often heavily polluted from river input so many fisheries are now lost. Salt marsh grasses, algae, phytoplankton, many invertebrates.

27. Marine environment with zonation.

28. Intertidal Zone: Alternately submerged and exposed by daily cycle of tides. Often polluted by oil that decreases biodiversity.

29. Coral Reefs: occur in neritic zones of warm, tropical water, dominated by cnidarians (corals); very productive, protect land from storms; most are now dying from rise in global temperatures
Neritic zones are shallow regions over continental shelves – beyond intertidal zone.

30. Deep-sea vent: Occurs in benthic zone; diverse, unusual organisms; energy comes not from light but from chemicals released from the magma.

31. Terrestrial Biomes Tropical rainforest Savannah Desert Chaparral
Temperate grassland
Temperate deciduous forest
Coniferous forest
Tundra

32. Distribution of Terrestrial Biomes

33. Terrestrial Biome Characteristics
Tropical Forest
Pronounced vertical stratification
Canopy trees make up most o f the upper stratum; little light reaching ground
Rainfall is major determining factor in types of plant growth
Savanna
Large herbivores and predators
Many insects
Grasses and scattered trees
Desert
sparse rainfall
temperature varies – cold at night, hot during day
animals and plants adapted to dry climate
Chaparral
dense, spiny evergreen shrubs
mild rainy winters, long hot summers
Temperate Grassland
prairies of N. Amer. are example
grasses, herbivores
Temperate Deciduous Forest
Deciduous trees
Sufficient moisture to support tree growth
Coniferous Forest
Cone bearing trees
Pacific NW
Taiga – Northern Coniferous forests; heavy snowfall during winter
Tundra
Permafrost
absence of trees
little annual rainfall
high winds and cold temperatures