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Summary Animal Ecology lecture notes
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Lecture Notes Animal EcologyEcology is complicated
- Many actors, interactions and feedback loops
- Pattern may become chaotic (need to focus on underlying processes)
Basic principles 1
- Feeding
- Not to be eaten
- Grow, develop and learn
- Reproduce
Basic principles 2
- All matter that contains energy will be used sooner or later
Basic principles 3
- Variation is self-sustainable
Species traits
- Limitations of the building plan at one hand
- And using the different types of variation at the other
a) tolerance (basic physiology)
b) learn to adapt (behavioral aspect)
c) phenotypical plasticity (on population level, not genetical) (reaction norms) – eg.
Larger leaves in shade
d) genetic variation (population effects)
Plasticity and genetic variation
- Variation in fitness
- Survival probability
- Natural selection
- Selection is only kept in the population when there is a genetical basis
Descriptive variation
- What do we see and what is happening? = demography
Genetical basis
- Quantitative genetics
- Which traits are subjected to variation?
- Singular genes or complex reaction norms
- Reaction norm: mapping of the genotype onto the phenotype as a function of the
environment
Trade offs
- Currency = fitness (survival)
- We often charge in energy
- Only when you are a grandparent you can be called fit (need to produce viable
offspring)
, Lineage specific effects
- The construction plan dictates the preconditions
… Different types of variation, but how does the environment select and what kind of
variation arises from the non-living environment?
Types of environmental variation
- Predictable (amplitude) – length of night
- Predictable but with unpredictable amplitude – length snow cover
- Unpredictable
Predictable
- Seasons due to rotation around the sun and the tilt of the axis of rotation
- Day and night rhythm due to rotation around own axis
- Rotation around the moon in combination with the Earth-Sun position leading to tidal
rhythm
- Attenuation (verzwakking) of the amplitude: due to distance Sun and Earth and the size
of the Earth (gravity), there is a lot of water in the liquid phase on the Earth =
temperature fluctuations (2/3 covered with water! And high temperature capacity); also
further equalization of temperature differences due to horizontal and vertical flow (air
and water)
Unpredictable
- Large scale, volcanoes: ash = drop in temperature can last for many years
- Smaller scale, flooding, extra hot or cold periods out of season and periods of drought
- Attenuation of the amplitude: vegetation layer dampens in many area differences in
temperature and moisture content (desert: great differences in temperature during day
and night): removal can have irreversible effects (dry out)
Relation environmental variation and life history
- An individual only experiences the cycle of environmental variation when the lifespan
exceeds the cycle
- A tide cycle is already too long for a bacterium
- Comparison of life history is always relative: related species have brood care, different
sized eggs, etc.
- With one generation per environmental cycle, each generation will have to survive the
unfavorable time: have an obligatory adaptation
- Optional/facultative for several generations per cycle
Classifications of biotopes, habitats
- Distinguish between predictable and unpredictable
- Cyclical or non-cyclical in time
- Continuous, fragmented or isolated in space
Quadrant of Southwood
,MacArthur and Wilson
- More from a species perspective
- R-select: rate of increase
* Aphids: large amount of young and short generation time
- K-select: carrying capacity
* Albatross: few young, takes good care of young, takes a long time to mature and lives
long
- With sophistication (by Grime)…
- R: many seeds, disperse easily
- C: little seeds, slow spread, but when established its long living
- S: combination
- R is fairly defined as the intrinsic rate of increase
- K is difficult to measure and is dependent on various aspects of the environment: food
availability may vary over time (not constant)
- C has no measurable value
- S is measurable, but very diverse and the comparability is in the reaction of the species
= environmental classifications result in poorly defined concepts
= for a good life history approach, we therefore use the traits of the species, which are
related to the mentioned variation in the environment, on which the species invest
relatively strongly: trade offs
Balance between income and expenditure
- Investing in traits costs energy (fitness)
- Energy must first be obtained
, - A small part is given by the parents (eggs, brood care)
Niche
- Multidimensional space of environmental factors (resources), where the parameter
range is given at each environmental factor
- In the absence of other species, the parameter values represent the fundamental niche
- Competition will lead to some limitation of the parameter values which will be realized
on some of the dimensions leading to the realized niche
- The greater the competition, the narrower the niche
Specialist and generalist
- Generalist species have a narrower niche width on some of the dimensions
- Specialism arises under pressure from competition
- The niche width is divided
- A generalist has a larger niche width on most of the dimensions
Habitat
- The subset of the niche referring to the place of residence of the species
- The effectiveness of competition depends in part on the mobility of the competing
species in relation to their individual lifespan
- Competitive exclusion only takes place if the species is very mobile
Advantage of specialization
- Limited investment in digestive enzymes (only the ones that are needed)
- Defusing the defense mechanisms or substances of the plants
- But disadvantage: limited in the amount of food
Trade off
- A trick or trait costs extra energy
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