Introduction to Ecology
Areas of Ecological Study
In ecology, researchers work at four main levels: organisms, populations, communities, and ecosystems.
Organismal ecologists explore the morphological, physiological, and behavioural adaptations that allow individuals organisms
to live successfully in a particular area.
o Behavioural ecology
o Eco physiology= physiological ecology of plants and animals
o Reproductive ecology of plants and animals.
A population is a group of individuals of the same time species that lives in the same area at the same time.
Population ecologists focus on how the numbers of individuals in a population change over time.
o Life history trade-offs between survivorship and reproduction.
o Age structure of populations
o Modeling of competition, predation, and host-pathogen interactions.
o Modeling of fisheries and other natural harvest.
A biological community consists of the species that interact with one another within a particular area.
Community ecologists study the nature and consequences of the interactions among species in a community.
At this level, ecologists also analyze how groups of species respond to natural disturbances such as fire and flood.
An ecosystem consists of all the organisms in a particular region, along with non-living, or abiotic, components.
Ecosystem ecologists study how nutrients and energy move among and between organisms and the surrounding atmosphere
and soil or water.
Because humans are affecting energy flows and climate, this work has diet public policy implications.
How do Ecology and Conservation Efforts Interact?
The four levels of ecological study are synthesized and applied in conservation biology.
Conservation biology: the effort to study, preserve and restore threatened populations, communities, and ecosystems.
Conservation biologists prescribe remedies for threatened species and managed land to produce a diversity of species,
clean air, pure water, and productive soils.
The study of interactions between organisms and their environments.
The study of plants and animals at home, that is to say, in their natural environment (from the Greek word oikos, a house).
Quantitative natural history.
The study of complex systems where we sees the consequences of many forces each of small effect.
An interdisciplinary approach to biological systems
o Economics arises from the same Greek work oikos and literally means “household management”
Ecology is a Young Science
Late 1800‟s in Europe
History affects how the science is structured
o Some separation from genetics and evolution
o Separation between plant ecology and animal ecology
History of Attempts To Make Ecology A Rigorous Science
Using Latin terminology: A 1905 ecology book defined the geotome as “an instrument for obtaining soil samples” (shovel).
Physics envy: search for universal laws
Hypothesis testing- null hypothesis-ignores the importance of description
Ecology and Statistical Methods
Statistics are an integral part of ecology
Ecology is a young science about complex systems with many interacting factors of small effect.
Scientists (in their own field, anyway) consider that there are NO facts. Rather, there is evidence, and there is interpretation.
In ecology, undergraduates can also evaluate the evidence and its interpretation.
Plant Behaviour Introduction
Behaviour is action- a response to a stimulus.
Behavioural biology is essentially ecological. Ecology is the study of how organisms interact with their physical and
biological environments, and behavioural biology is the study of how organisms respond to particular stimuli from those
Proximate (or mechanistic) causation explains how actions occur. Ultimate (or evolutionary) causation explains why actions
Efforts to explain behaviour at the proximate and ultimate levels are complementary.
After describing behaviour, biologists, seek to explain both its proximate and ultimate causes-meaning, how it happens at the
genetic and physiological levels and how it affects the individual‟s fitness.
Introduction to Ecology
In a single species, behaviour may range from highly stereotyped invariable responses to highly flexible, conditional responses
and from unlearned to learned responses.
Fixed action patterns (FAPs) are highly stereotypical behaviour patterns that are usually triggered by simple stimuli called
signal stimuli or releasers.
FAPs are example of innate behaviour, behaviour that is inherited and shows little variation based o learning or the
Innate behaviour is commonly observed in response to:
o Situations that have a high impact on fitness and demand a reflex-like, unlearned response
o Situations where learning is not possible
Conditional Strategies and Decision Making
Although all species how some degree of innate behaviour, it is much more common for an individual‟s behaviour to change
in response to learning an to show flexibility in response to changing environmental conditions.
Animal appear to take in information about their environment and make choices after weighing the costs and benefits of
responding in various ways.
Costs and benefits are measured in terms of their impact on fitness-the ability to produce offspring.
Plants „behave‟, but very slowly through developmental plasticity.
Plant „behaviour‟ can be condition-dependent.
Traits can be genetically based, but expression depends on environment.
Acclimation to differing environments
o How traits change with the environments also has a genetic basis.
o This concept is crucial to understanding human evolution.
The Evolution of Self-Sacrificing Behaviour
Altruism is behaviour that has a fitness cost to the individual exhibiting it and a fitness benefits to the recipient of the
Altruism decreases an individual‟s ability to produce offspring but helps others produce more offspring.
The existence of altruistic behaviour appears to be paradoxical, because if certain alleles make an individual more likely to be
altruistic, those alleles should be selected against.
Selfish behaviour, like being competitive, does make good evolutionary sense. Being less selfish with related individuals is the
corresponding evolutionary paradox.
Hamilton’s rule shows that individuals can pass their alleles on to the next generation, not only by having their own offspring
but also by helping close relatives produce more offspring.
Hamilton‟s rule states that if the benefits of altruistic behaviour are high, the benefits are dispersed to close relatives, and if the
costs are low, alleles associated with altruistic behaviour will be favoured by natural selection and will be spread throughout
This rule can be expressed as Br>C, where B is the fitness benefit to the beneficiary, r is the coefficient of relatedness, and C
is the fitness cost to the actor.
o Note that there is no animal bias to Hamilton’s rule
Kin selection is natural selection that acts through benefits to relatives.
As an example, Figure 51.22 illustrates experimental evidence that black-tailed prairie dogs are more likely to give alarm calls
if relatives are nearby.
The patterns of altruistic behaviour toward kin have been observed in many other species of social mammals and birds.
Selfishness is another trait under kin selection. Hamilton argued that kin selection favours directing selfish behaviours at
unrelated individuals. An animal example is cannibalistic spadefoot toad tadpoles that avoid eating relatives.
Scientific Evidence That Plants Have A Secret Social Life
Plants often live closely with relatives.
An individual‟s fitness depends on the characteristics of the group.
Plants demonstrate phenotypic plasticity to other plants-analogous to behaviour.
Plants grown in close proximity, closer together than animals do. They live with other species, strangers of their species, and
Why Do Any Organism Recognize Their Relatives?
o Known in animals and plants
Favour relatives in social interactions
o Known in animals but not previously in plants
Phenotypic Plasticity In Response to Neighbours
Plants do have “competitive behaviours”
Plants use phenotypic plasticity to neighbours to increase their competitiveness
o Stem elongation in response to R:FR
Introduction to Ecology
o Root plasticity to neighbouring roots
Plants have been shown to respond to the presence of neighbouring plants by increasing their biomass allocation to roots.
Root allocation is arguably a competitive traits, since plants with more roots can pre-empt water and nutrients.
We Will Examine 1st Aquatic and 2nd Terrestrial Ecosystems
An organism‟s environment has both physical (abiotic) and biological (biotic) components.
The abiotic components include such factors as temperature, precipitation (terrestrial), salinity (aquatic), water depth
(aquatic), wind or current strength, and sunlight.
The biotic components consist of other members of the organism‟s own species, as well as individuals of other species
This chapter focuses, on a global scale, on how the physical (abiotic) environment varies, and how that affects communities.
However, species distribution is also constrained by historical and biotic factors.
Physical structure: particularly water depth- is the primary factor that limits the distribution and abundance of aquatic
Climate: specifically, both the average value and annual variation in temperature and moisture- is the primary factor that
limits the distribution and abundance of terrestrial species.
Organisms Experience Different Challenges In Air vs. Water
In water in highly available. However, osmoregulation is an issue, freshwater is more dilute than „normal‟ cells, saltwater ore
Water is denser than air
o Organisms have buoyancy in water, but must cope with gravity in air.
Air is 21% oxygen, but concentrations are lower and more variable in water. Oxygen diffuses more rapidly in air.
Water changes temperature more slowly than air
Water reduces light availability
Physical Factors Play a Key Role in Aquatic Environments
Water depth ad the rate of water movements are the key physical factors that shape the environments in aquatic ecosystems.
Water depth dictates how much light reaches the organisms that live in a particular region. The amount and types of
wavelengths available to organisms change dramatically as water depth increases.
Light has a major influence on productivity- the total amount of carbon fixed by photosynthesis per unit are per year.
The type and amount of water flow also have a major influence in aquatic environments.
Communities also are strongly affected by salinity, with distinct communities in freshwater, saltwater, and brackish water.
Freshwater Environments: Lakes and Ponds
Lakes and ponds are distinguished by size-ponds are smaller than lakes.
Lakes and ponds have different habitats that depend on depth and light penetration:
o The littoral zone consists of the shallow waters along the shore, where flowering plants are rooted.
o The limnetic zone is offshore and comprises water that receives enough light to support hypothesis.
o The benthic zone is made up of the bottom, or substrate.
o Regions of the littoral, limnetic, and benthic zones that receive sunlight are part of the photic zone.
o Portions of the lake or pond that do not receive sunlight make up the aphotic zone.
Wetlands are shallow-water habitats where the soil is saturated with water for at least part of the year.
Wetland types are distinguished by water flow and vegetation. Water flow in bogs is low or non-existent. Freshwater marshes
and swamps are characterized by a slow but steady flow of water.
Wetlands have emergent vegetation- plants that grow above the surface of the water. Bogs are not productive, unlike marshes
and swamps; marshes lack trees and typically feature grasses, while swamps are dominated by trees and shrubs.
Streams are bodies of water that move constantly in one direction. Creeks are small streams, rivers are large.
Most streams are shallow enough that sunlight reaches the bottom.
The structure of a typical stream varies along its length. Where it originates, it tends to be cold, narrow, and fast; at the end, it
tends to be warmer, wider, and slower.
As a result, streams tend to have fewer types of organisms near their source (mostly animals) and more varied types near their
end (algae, plants, and animals).
An estuary forms where a river meets the ocean and freshwater mixes with saltwater.
Most estuaries are relatively shallow, but water depth may vary dramatically.
Water flow fluctuates daily and seasonally dues to tides, storms, and floods. This fluctuation alters salinity.
Species that live in estuaries have adaptations that allow them to cope with variations in salinity. Estuaries are among the most
The world‟s oceans form a continuous body of salt water. Regions within an ocean can vary markedly in their physical