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Summary Introduction to Animal Ecology
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lOMoARcPSD|2392027, lOMoARcPSD|2392027
Ch1: Ecology & how to do it
Book
1.1 Introduction
What is ecology => how do we define ecology?
Definition: scientific study of distribution & abundance of organisms & the interactions that
determine distribution & abundance
Coexistence of applied & fundamental (pure) science
- Applied: apply knowledge for own collective benefit
Many questions remain unanswered
Complex science due to uniqueness: different species, genetically different individuals ->
all living & interacting in changing world
- Seek patterns & predictions within complexity
What ecologists try to do:
1. Understand: explain science
2. Describe: before they explain
3. Predict & control
Classes of explanation
1. Proximate
- Why?
- Explain distribution & abundance of species in terms of: physical environment, food
& predators
- What is going on here & now
2. Ultimate
- How?
- Explanation in evolutionary terms
- How did organism get these properties
- Explanation of distribution & abundance lies in ecological experiences of its
ancestors (ch2)
Description => describe what we wish to understand
Directed description
Prediction => what will happen to population of organisms under particular set of circumstances
On basis of these predictions: control, exploit or conserve population
1.2 Scales, diversity & rigor
Ecological phenomena occur at variety of scales
Ecological evidence comes from variety of sources
Ecology relies on truly scientific evidence & application of statistics
, lOMoARcPSD|2392027
Questions of scale
Biological scale (hierarchy):
1. Individual organisms
2. Populations (individuals of same species)
3. Communities (several
populations) Focus on pathways:
4. Ecosystems (community with physical environment)
Range of spatial scales
- Every area (small & large) has an ecology
- 1 cell – gut – rain forest – atmosphere
- Fleas on different bird species – birds in different sized patches of woodland –
woodlands at different altitudes
Range of time scales
- Related to biological hierarchy & range of spatial scales
- Ecological succession (colonization by certain species, accompanied by extinction
of others) => may be studied over different periods of time
- Days – weeks – years
- Appropriate time scales vary
- Need for long-term studies => great value to ecology, but: cost more & require
greater dedication
Diversity of ecological evidence
Ultimately: ecologists interested in organisms & their natural environment
1. Observations & field experiments
- Monitor changing abundance of species over time or space (or both)
- Establish patterns
- Patterns require explanation: analysis of descriptive data and/or manipulative
field experiments
2. Laboratory experiments
- Field experiments costly & difficult, natural field systems may be too complex
- Controlled laboratory experiments often best way to provide answers to specific
questions that are key parts of overall explanation of complex situation in the
field
Simple laboratory systems => basic understanding of simpler communities
3. Mathematical models
- Analysis of ecological communities: constricted & manipulated
Major aim of science is to simplify, but eventually it is the real world we are interested in
- Models & simple laboratory experiments must be judged on similarity on working
of more natural systems
Statistics & scientific rigor
Ecology => search for conclusions in which we can be confident
- No search for statements that have been proven to be true
- Nothing proven with statistics, not what it if for
, lOMoARcPSD|2392027
- Statistical analysis essential for attaching level of confidence to conclusions that can
be drawn
- Science is based on conclusions that are results of investigations carried out with
purpose of deriving those conclusions & to which level of confidence can be
attached (measured on agreed scale)
Ecologists must think ahead
- Statistical analysis carried out after data collection, help interpret data
- Know how they are going to analyze data statistically, not only after & while
collection, but even before they begin to collect it
- Plan: right kind of data & sufficient amount of data -> to address questions they hope
to answer
Ecology relies on obtaining estimates from representative samples
- Draw conclusions about groups of organisms overall (birth rate bears Yellowstone park)
- Almost impossible to sample every individual or entire area -> rely on
representative sample from group/habitat
1.3 Ecology in practice
3 main points:
- Ecological phenomena at variety of scales
- Ecological evidence from different sources
- Ecology relies on scientific evidence & application of statistics
Brown trout in NZ: effects on individuals, populations, communities & ecosystems
Most studies focus on 1 out of 4 levels in biological hierarchy (individuals,
populations, communities, ecosystems)
- However: understanding enhanced when links between levels are made clear
Introduction of exotic fish to streams in NZ
1. Individual level: consequences for invertebrate feeding behavior
- Daytime activity reduced with both fish, but to greater extent when trout is present
- Invertebrates in trout stream more at risk of predation during daylight
2. Population level: brown trout & distribution of native fish
- Where do trout & native species occur?
- Trout directly affects native species distribution (predation)
3. Community level: brown trout causes cascade of events (several populations of
different species)
- Changes also cascade through to other species
- Trout reduce invertebrate biomass, presence of native species did not
depress invertebrate biomass (invertebrates eat algae)
- Algae biomass indirectly increased in presence of trout -> reduction in
invertebrate density & restriction of grazing behavior of invertebrates
4. Ecosystem: trout & energy flow (community with physical environment)
- Hypothesis: rate at which radiation energy was captured through photosynthesis
by algae -> greater in trout stream compared to native fish stream
- Trout stream -> fewer invertebrates -> lower algae consumption rate
- Primary production by algae indeed 6x higher in trout stream
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