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Summary Introduction to Animal Ecology

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Summary of the exam material: book, knowledge clips & tutorials

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  • Hoofdstukken van dit vak (tentamenstof)
  • February 17, 2022
  • 91
  • 2019/2020
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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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