This document contains all lecture notes from the lectures of REG-21306. It also contains a summary of chapters for the book 'essentials of ecology' fourth edition, Wiley, linked to the lectures. My summaries are usually concise and do not contain detailed explanation of examples mentioned in the b...
Introduction to animal ecology
Information from presentations
Summary of the book
Tutorial
Said to be of importance for the exam
Terminology
Term and definition
Lecture 1
Presentation
Ecology looks at an animal in their environment. Animal husbandry can improve or deteriorate
animal performance. Most terrestrial biomass is taken up by cattle. Next humans, sheep pigs, pets,
goats, wild animals and last horses.
Natural systems have a higher biodiversity than manmade ones.
Self-test is very similar to the actual exam.
Ecology starts when you take the environment into account. Why does the animal occur here? Is
there competition between the species? Why/Why not? Social organization, number of species etc.
Trait = what an animal looks like outside and in. (adapted to environment)
Ecology model: look at an organisms and their environment. Both influence each other. What is the
explaining and what is the dependent factor?
How is the animal influenced/how is the environment influenced?
What makes an animal different from a plant? What are animals in the first place?
Animals started in water and evolved onto land. Animal variety is rather big, the view of what an
animals is, is biased. This course is mainly about vertebrates. Most animal species are fish, mammals
are a small part.
Plants and animals have a different cell makeup. Animals have no cell wall and plants have a vacuole
etc.
A difference between plants and animals is intelligence (having a brain). However you can interact
with plants as well as animals.
Animals can move. Plants move on a time scale that is barely noticeable.
Animals are very fixed in how their body develops. Plants can adapt all the time. Plants can be all
genetically the same. Animals are fixed and singular/unitary. Plants can change their form, animals
cannot. Plants are modular, vertebrates are unitary.
Animals do not have chloroplasts (cannot photosynthesize). They cannot produce energy themselves,
they have to feed on other organisms.
Animal ecology interests:
- Life history
- Physiology and behavioral thermoregulation
- Migration
- Foraging
- Food webs and trophic cascades
- Group dynamics
- Mate selection
- Parental behavior
A typical ecology question is ‘what explains variation?’
Quite often females are responsible for male external features.
For the exam you should be able to differentiate between different levels, like ecosystem or
individual level.
,Environment changes and fluctuates. Climate change, weather etc. all influence it.
We work on three scale levels:
- Individuals: traits.
- Populations: density.
- Communities: structure.
Essentials of ecology
1.1
Applied ecology: seeking to understand the distribution, abundance and productivity of organisms in
order to apply that knowledge for their own benefit.
Ecology is complex because of its uniqueness (many species in everchanging environments).
An explanation is proximate (what is going on here and now) or ultimate (evolutionary explanation).
1.2
Levels:
- Population
= functioning group of individual organisms of the same species in a defined location
- Community
= all the populations present in a defined location
- Ecosystem
= both the community and the physical environment in which they exist
- Biosphere
= totality of all life interacting with the physical environment at the scale of the planet
Three generalities:
1. Properties of one level arise from the parts of the level below.
2. To understand a certain level, the organization of the next lowest level has to be understood.
3. Properties may be predicted without fully understanding them.
,Ecological succession: successive and continuous colonization of a site by certain species populations,
accompanied by the local extinction of others.
Ecology can also be studied on different time scales.
Tools for ecological evidence:
- Observations.
- Experiments.
- Mathematical models.
Using these methods patterns can be observed. With manipulative field experiments hypotheses
can be tested. (treating sick animals or changing the environment and observing the results of the
change)
Comparative field observations can also be used. The same data is gathered from different sites.
Statistics can be used to test if differences or changes are significant. Field experiments are costly,
complex and difficult to carry out. Lab work and mathematical models are easier and cheaper.
Mathematical models are used when creating the wanted ecological environment is very difficult or
impossible.
Science is based on conclusion derived from thoroughly tested hypotheses. Statistics help interpret
found data.
Ecologists must think ahead. (know what you are doing before doing it)
Replications improve statistical significance of an experiment.
There is a trade-off between realism and replication. You can do few very realistic experiments or
simplified experiments in high amounts.
Information about 1 experiment situation should be representative for many real others.
1.3
General points about mathematical models in ecology:
- Models can be used when it is not possible to obtain real data.
- They can summarize current knowledge.
- A model does not have to be perfect and complete to work.
- Because models aren’t perfect caution is necessary.
- A model can be applied with more confidence if it’s been supported with real data.
Common garden: multiple species from different sites are brought together and monitored under
same circumstances.
Translocation experiment: a species is moved from one location to another and the impact of this on
population size etc. is monitored.
,Lecture 2
Presentation
Questions can be proximate or ultimate.
Proximate: organism level & physiology. How?
Ultimate: species level & evolutionary advantages. Why?
Evolution = change of life forms over time, this change is inevitable
Three components of evolutionary change (driven and influenced by time and space):
Variation within a population
Inheritance of variation
Differential reproductive success and difference in inherited variance.
When a population splits up, random variation will cause them to diverge. Speciation can be a mere
outcome of isolation.
Speciation can happen by chance.
Ecological speciation: interaction with environment. (the environment steers evolution)
Allopatric and sympatric.
Allopatric is in a different area, sympatric is in the same location.
Speciation timeline: allopatric isolation, secondary contact, sympatric isolation.
Two diverging species can come into contact with each other again. If isolation before secondary
contact is strong enough speciation occurs.
Evolution can diverge, converge and be parallel. Divergent evolution is when species start to differ
from each other but have a same ancestor. In converged evolution species become similar in the
absence of a common ancestor. Parallel is species with the same ancestor in different locations
evolve the same.
Is a given example divergent, convergent or parallel?
Only if in the here and now a trait has an advantage there is a fitness advantage. Past changes can
influence future possibilities for change.
Evolution is like saving a game in between when playing it. If you die you don’t have to start over.
You start where you left of.
In evolution there is a lot of contingency. What you have now determines the possibilities for what
you might be able to get in the future.
Climate change is strongly liked to species richness in an area. Heavy glacial periods will decrease the
amount of species surviving. In the Pleistocene glacial periods occurred.
Humans also influenced which species occur where. Dog breed variety stemming from wolfs show
the potential and power of selection.
How to know if animals adapted or changed by chance:
, - Correlation: do spatial patterns line up with trait variation (Looking at trait similarity across
areas)
- Experimental: transplant experiments.
Analogous = same function
Homologous = same ancestor
If evolution is from a common ancestor and animal traits are alike? Parallel.
No common ancestor and same traits? Convergent.
Some animals seem to function the same but if you take the animals out of their environment and
you put them in a different one you’ll see their adaptation = counter gradient variation. (Tadpoles
develop at same speed in different environments. Experiment showed that tadpoles form different areas at different
temperatures developed faster or slower. The environment influenced how fast the tadpoles developed in correlation to
temperature.)(a+x = b+y)
Essentials of ecology
2.1
Darwin coined the theory that species evolve from one another as a result of natural selection. Alfred
Russell Wallace helped further develop the evolution by natural selection theory. It rests on a series
of established truths:
1. Individuals that form a population of a species are not identical
2. Some of the variation between individuals is heritable.
3. All populations could grow at a rate that would overwhelm the environment. However most
individuals die before reproducing.
4. Different ancestors leave different numbers of descendants. Those that contribute most have
the greatest genetic influence.
Evolution is the change in heritable characteristics of a population or species.
2.2
Carl Linnaeus devised a system for naming organisms. Natural selection does not only create species,
it occurs within them.
Population characteristics will only diverge if there is sufficient heritable variation and if the forces
driving selection are strong enough to counteract mixing of individuals from different sites.
Counter gradient variation = phenotype variation from genes is different from phenotype variation
caused by environment. (Ectotherms grow at a slower rate as latitude increases due to this impact of temperature.
However, under counter gradient variation, when these same animals are placed in a common environment with their low-
latitude relatives, they grow faster relative to the low-latitude population.)
hybridization = the production of offspring sharing the characteristics of two parents.
Reciprocal transplant experiment: comparing performance in a natural and new environment.
However from species in their natural habitat some may simply be fitter than others, regardless of
where they’re transplanted to.
Correlation does not equal causation.
Pollution can cause powerful selection.
Coevolution = evolution where predator and prey or cohabitants in an environment influence the
evolution of one another.
Coevolution can be antagonistic or mutualistic.
2.3
Species: individuals can breed together and produce fertile offspring.
Species tested and defined this way are biospecies. One species can only evolve into two if there is a
barrier between gene flow. Ecological speciation requires divergent selection and reproductive
isolation.
Speciation stages:
1. Two subpopulations become geographically isolated, natural selection drives genetic
adaptation towards the local environment.
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