How to get more from readings

SECTION 1
Chapter 1

Chapter 2

Chapter 3
Chapter 22
Chapter 4
Chapter 5

SECTION 2
Chapter 6
Chapter 7

Chapter 8
Chapter 9
Chapter 10

Chapter 20

SECTION 3
Chapter 11
Chapter 12
Chapter 13
Chapter 14
Chapter 15
Chapter 16
Chapter 17

SECTION 4
Chapter 18
Chapter 19
Chapter 21

Chapter 23

This chapter is basically a review of the ecological principles you should already know from your biology or ecology classes. However, this chapter is important in that you need a thorough grounding in these concepts because wildlife science is the application of ecological principles to the wildlife concerns of people.

Ecosystems are self-sustaining networks of living (biotic) and non-living (abiotic) elements that interact to sustain life. Living parts of an ecosystem are called communities and usually consist of many different species. Each species in the community plays a role in that community. Most ecosystems consist of several different communities that we can identify. Ecosystems can be modified by internal (changes in species composition or species interactions) or external (changing weather, volcanoes etc.) factors. Wildlife management is concerned primarily with anthropogenic (human made) external factors that affect ecosystems. Wildlife managers often manipulate factors affecting ecosystems intentionally to achieve a desired goal. We have learned much since the 1960's about interrelationships within communities and ecosystems but there is still much we do not know. Modern wildlife management operates to maintain the total community in a functional self-sustaining ecosystem.

1. Matter and energy
   1. all organisms (plants and animals) are made of materials (matter) that occur in the physical environment of earth.
      1. carbon atoms are the basis of life on earth
      2. phosphorus, calcium, potassium, sulfur, iron, and all the trace elements that form plant or animal bodies enter in the form of food (nutrients) except oxygen which enters through breathing
   2. green plants form the crucial link between the biotic and abiotic world
      1. they can remove carbon from carbon dioxide in the air through photosynthesis. They also produce organic compounds (carbohydrates, sugars, etc.) that store the energy of sunlight in chemical compounds.
      2. the only exceptions to date are some unique communities that function through chemosynthetic energy and sulfur compounds surrounding volcanic vents in the ocean floor.
   3. Trophic levels and food chains or webs
      1. trophic levels relate to how organisms obtain energy and nutrients
         1. plants are primary producers (changing solar energy and chemical compounds into carbon based compounds useable by animals) this is the 1^st or bottom trophic level.
         2. animals are consumers. Herbivores eat plants and are therefore, the 1^st or primary consumers. Carnivores eat other animals and are therefore, the 2^nd or secondary consumers. Animals that eat only animals that ate only other animals are rare and are called tertiary consumers.
      2. food chains are the pathways for nutrients to flow through ecosystems.
         1. primary producers (plants) primary consumers (herbivores) secondary consumers (carnivores) and finally for all life, decomposers
         2. interactions among species in a community are seldom linear (usually multiple pathways for energy to flow) so we more frequently speak of food webs. (see Fig. 4-2 in text)
      3. energy is necessary for all life.
         1. 2^nd law of thermodynamics states that the transformation of energy is not 100% efficient.
            1. progressively lesser amounts of energy are available at each trophic level
         2. empirical evidence has suggested a 10% rule; that only 10% of the energy in a trophic level is converted to energy at the next higher level. (see Fig. 4-3 in text)
            1. this limits the total number of trophic levels possible (most ecosystems only have 3-4)
2. Range of tolerance
   1. Environments vary widely: temperatures, moisture, amount of salt etc. can be very different in different parts of the world and even between some places that are very close together.
   2. A single species does not exist everywhere. There is usually a range of environmental conditions that it can live in.
   3. Different species can tolerate different ranges of environmental conditions
      1. species that can tolerate narrow ranges of conditions are steno -typic
      2. species that can tolerate wide ranges of conditions are eury -typic
   4. Individual persistence (won't die immediately), individual survival (can live successfully), and population survival (pop. can continue over time) may require different environmental conditions or Ranges of Tolerance (see Fig. 4-4 in text).
3. Niche
   1. niche differs from habitat
      1. habitat is where an organism lives (its address): it consists of the suitable arrangement in space of the necessary food, water, and cover for the organism to survive
      2. niche is how an organism lives (its profession): many different organisms may live in same environment (~habitat) but, competitive exclusion ensures that each species fills a different functional role in the multi-dimensional environment (e.g., time, space, food, water, and cover).
   2. species may have niches of different widths
      1. generalists can use a wide range of habitats in many different ways - have wide niches
      2. specialists use only specific habitats in specific ways - have a narrow niche.
   3. competitive exclusion principle
      1. 2 or more species with the same requirements (highly overlapping niches) cannot co-exist on the same resource. One population will always out compete the other.
      2. where its' resources exist a specialist may out compete the generalist, but where those specific requirements aren't quite right the generalist will out compete the specialist.
   4. ecological equivalents
      1. species that use similar niches in different habitats or locations are called ecological equivalents
      2. the evolution of life has resulted in general types of habitats and certain successful ways of exploiting the resources in those habitats. Parallel evolution has resulted in unrelated species that have similar niches in different environments.
   5. the ability to match habitats to the niche requirements of a species is fundamental to successful wildlife management.
   6. Niches are of particular concern when manipulating environments or changing species occurrence in environments. Introduction of a new species or removal of some existing species may alter the relationships between niches in the community, displacing or eliminating the niches of species that already occur in the community.
4. Natural communities - changes in time and space
   1. Communities that are similar (consist of ecological equivalents) occur throughout the world. Spatial patterns of communities result from different climates on earth (e.g., tropics vs. arctic). We group communities of similar types from across the globe together as biomes.
      1. biomes classifications are based primarily on temperature and precipitation gradients.
         1. latitude, altitude are the major physiographic features that affect temperature and precipitation
   2. Composition of natural communities also changes with time.
      1. succession is the relatively sequential process of changes in community (usually described by the plant community) composition through time.
         1. primary succession - occurs when biotic communities develop where no community existed before (e.g., on new volcanic islands etc.)
         2. secondary succession - occurs when there are remnants of a previous community (e.g., when forest is cut secondary succession occurs as the new forest grows from the remnants of what was left)
      2. succession progresses through stages
         1. pioneer community - first step in succession
         2. early (or young) seral stages - occur as communities begin to develop on a site but will not persist as succession progresses
         3. mid-seral stages - occur between early seral and climax stages
         4. climax stage - communities are self-perpetuating. This means that, if left undisturbed, this community will maintain the same composition over time (dynamic equilibrium).
      3. If the successional process is left undisturbed long enough over time, all communities will eventually succeed to their climax stage.
         1. climax = different communities in different biomes
            1. in arctic systems, lichens, grasses, forbs (tundra) may be the climax stage
            2. while, in temperate forests the arctic climax is an early seral stage on the successional pathway to perhaps a deciduous hardwood forest.
         2. disturbance (changes in the environmental factors affecting the community) alters succession.
            1. natural disturbances have always occurred (e.g., fire, flood, tornado etc.)
            2. human caused disturbances also affect succession (grazing, forestry, plowing etc.)
5. Succession and wildlife management
   1. Succession is one of the most important concepts in wildlife management.
      1. within their range of tolerance, different wildlife species are associated with different successional stages (see Table 4-2 in text)
      2. much of wildlife management deals with ways of manipulating succession to create habitat for the benefit of selected species.
   2. Recall, that if they are not manipulated, successional communities will change on their own progression towards climax. Many desired wildlife species prefer early or mid-successional stages. Management of disturbances is required to maintain those habitats in successional stages favorable to the desired species.
   3. Most human actions (intentional or not) result in disturbances that alter succession away from climax conditions.
6. Diversity and stability
   1. diversity relates to the number of different species in a community.
      1. species richness (alpha diversity) relates to # of different species in the community
      2. species eveness is the extent to which all species in the community are equally abundant, rather than 1 or 2 species being very common and the others very rare.
   2. stability is the ability of an ecosystem to return to its steady state (the same composition) in the face of disturbance.
   3. There is still argument over whether diversity creates stability or vice-versa. However, there definitely is a correlation between the two and more complex, more diverse, communities are generally more stable (fluctuate less) than less diverse communities.
   4. Effective wildlife management involves recognition of the degree to which communities are disrupted when plant and animal communities are altered (either intentional manipulation = management; or unintentional manipulation as a by-product of human activities).