Introduction to Ecology
Session 1 – Introduction to the
Study of Ecology
The Science of Ecology
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Goals for the day
Differentiate Between Ecology and
Environmentalism and Conservation Biology
Trace History of Ecological Thought
Define Ecology Scientifically
Determine factors determing species
distribution
Organization of Ecology
The Science of Ecology
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•
•
•
•
Goals for the day
Differentiate Between Ecology and
Environmentalism and Conservation Biology
Trace History of Ecological Thought
Define Ecology Scientifically
Determine factors determing species
distribution
Organization of Ecology
Key Distinctions
• Ecology is a science
– Our focus in this course
• Environmentalism is a cause
– With or without scientific backing
• Conservation Biology is the integration of
these two
– Using science to support a political cause
The Science of Ecology
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•
•
•
•
Goals for the day
Differentiate Between Ecology and
Environmentalism and Conservation Biology
Trace History of Ecological Thought
Define Ecology Scientifically
Determine factors determinig species
distribution
Organization of Ecology
History of Ecological Thought
• From Thoreau to
modern times
• Historically has been
literature-based
appreciation of
nature
• Subsequently
became more of a
descriptive science
Darwinian References
• “…how infinitely
complex and closefitting are the mutual
relations of all
organic beings to
each other and to
their physical
conditions of life.”
– Origin of Species
The Science of Ecology
•
•
•
•
•
Goals for the day
Differentiate Between Ecology and
Environmentalism and Conservation Biology
Trace History of Ecological Thought
Define Ecology Scientifically
Determine factors determinig species
distribution
Organization of Ecology
Definition of Ecology
• “To determine the factors that have
produced the present distribution
and abundance of organisms”
– (Jonathan Krebs, 1972)
Ecology-Defination
Interactions (organisms and environment)
determine distribution and abundance of
organisms.
Two main themes in ecology are:
- Where do organisms live? & Why?
- How many organisms are present? &
Why?
Types of ecosystems
• Terrestrial (land)
• Aquatic (water)
– lotic -rivers, running waters
– lentic-standing waters, lakes and resoivoirs
• Lentic ecosystems
– Lakes are empherel & accidental
– Great African lakes-centres of fish
biodiversity
• Lakes show thermal stratification
Aquatic and terrestrial biomes
(Biome = major ecosystem
type)
Oligotrophic Lake: Nutrient poor, water is clear, oxygen
rich; little productivity by algae, relatively deep with
little surface area.
Eutrophic lake: nutrient rich,
lots of algal productivity so
it’s oxygen poor at times,
water is murkier  often a
result of input of agricultural
fertilizers
Rivers and Streams: Organisms need
adaptations so that they are not swept away by
moving water; heavily affected by man changing
the course of flow (E.g. dams and channelstraightening) and by using rivers to dispose of
waste.
Wetlands: includes marshes, bogs, swamps,
seasonal ponds. Among richest biomes with respect
to biodiversity and productivity. Very few now exist
as they are thought of often as wastelands.
Estuary: Place where freshwater stream or river
merges with the ocean. Highly productive biome;
important for fisheries and feeding places for water
fowl. Often heavily polluted from river input so many
fisheries are now lost.
Aquatic biomes
Aquatic biomes cover about 75% of the earth’s surface
- Wetlands
- Lakes
- Rivers, streams
- Intertidal zones
- Oceanic pelagic biome
- Coral reefs
- Benthos
Lentic ecosystems
Thermal stratification
• Thermocline- plane of max temp
– Change from epilimnion towards the
metalimnion
• Winter-opposite happens- breakdown of
thermal stratification a Turnover
• Monomictic lake stratifies once a year
• Twice dimictic, many polymictic
Thermal stratification
• L Chivero is eutrophic polymictic
• L Kariba oligotropic monomictic
• If productivity is high and thermal
stratification occurs, oxygen depletion is
likely to occur in the hypolimnion in summer
Lentic ecosystem
• Lake stratification and mixing  alters
oxygen and nutrient levels. Dependent
on temperature changes and effect on
water density.
•
Ecology
• Ecology was historically an observational science, often
descriptive à natural history
• An organism’s environment has both abiotic and biotic
components.
• Abiotic components are nonliving chemical and physical
factors such as temperature, light, water, and
nutrients.
• - Biotic components are living factors such as other
organisms.
Ecology
• Ecology and evolutionary biology are closely related
sciences
• a. Events that occur in the framework of ecological time
(minutes, days, years) translate into effects over
evolutionary time (decades, millennia).
• Example: Hawks feeding on mice impact mouse
population and may eventually lead to selection for mice
with fur as camouflage.
Factors Influencing Organismal
Distribution and Abundance
• Abiotic
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–
–
–
Climate
Topography
Latitude
Altitude
• Biotic
– Intraspecific Interactions
– Interspecific Interactions
Behavior and habitat selection
• organisms do not always occupy all
available, suitable habitat
• may be specific in reproduction needs
• larval needs may be different from adult
needs
Biotic factors
• interactions with
other organisms
– Negative:
predation or
competition
– Positive:
facilitation
(e.g.,
pollinators
Fig. 50.9
urchin barrens
Biotic and abiotic factors: adaptations
Tolerate
Predation - Aposematic coloration
Dry conditions - cacti
Avoid
Predation – Cryptic coloration
Dry conditions – spring annuals
Biotic component
• Autotrophs- mainly palnts capable of converting solar energy and
inorganic material into organic energy-carbohydtrates, lipids and
other compounds through photosynthesis
• Known also as producers
• Heterotrophs (consumers)
– Animals and micro-organisms (mostly)
– Can’t manufacture food directly
– Eat palnts or other animals
– Three categoris- herbivores, carnivores and decomposers
• temperature
Abiotic factors
– high temperature cause cell
membranes to leak and
enzymes to stop working
– low temperature causes
freezing
- some animals have
antifreezes that allow
Fig. 27.1 – thermophilic bacteria, Nevada
them to survive below
freezing temperatures.
Cool arctic fish (spp.?)
Abiotic factors
• water availability
- too little water (desiccation)
- Deserts, saltwater
- too much water (anaerobic)
Mangroves
Organ pipe cacti, desert shrubs
Abiotic factors – Water availability
All terrestrial
organisms
Insects – tolerate, cuticle
Leaves, stomata
Worms – avoid, behavior
Abiotic factors – Water availability
And aquatic organisms too!
Freshwater
Saltwater
Abiotic factors
• Sunlight
- Competition, shade tolerance
for plants
- Photic zone, different
wavelengths for aquatic
organisms
Fig. 50.23
Abiotic factors
• Wind
– exacerbates the
effects of temperature
and water loss
– also exerts forces on
organisms (waves act
in the same manner)
krummholz
Abiotic factors
• rocks and soil
– substratum type
– nutrient availability
– pH
Combinations
of factors
• barnacle
distribution in the
intertidal-predation
from below,
desiccation from
above
Biomes
• Regions of the
earth that are
similar in organism
type although the
particular species
differ
• Driven largely by
climate – temp.,
water, seasonality
• Other factors –
soil, topography
Fig. 50.10 – Biomes of North America
Terrestrial Biomes
Determined by climate: latitudinal patterns;
local effects.
Vertical stratification based on vegetation.
Gradation in boundaries: ecotone.
Characteristic life forms.
Terrestrial biomes
- Tropical forest
- Savanna
- Desert
- Chaparral
- Temperate grassland
- Temperate deciduous forest
- Coniferous forest
- Tundra
World biomes
Fig. 50.24
World biomes – interactions among factors
• Latitude
• Seasons
• Atmosphere and
ocean circulation
patterns
• Mountains
Fig. 50.24
Biomes
Questions:
1. What are the dominant life forms in each biome?
2. What key factors limit the range of particular
biomes?
3. What key factors cause variation in conditions
within each biome?
4. What human impacts are particularly important
within each?
Microclimates
• within a biome, region or habitat, temp., water,
sunlight and other factors can vary dramatically
• these form small areas with microclimates or
microhabitats
• Can have strong effects on species ranges
Fig. 50.26
Example of Tropical, Dry
Forest
Desert: Sparse rainfall (< 30 cm per year), plants and animals
adapted for water storage and conservation. Can be either very,
very hot, or very cold (e.g. Antarctica)
Chaparral: Dense, spiny, evergreen shrubs, mild
rainy winters; long, hot, dry summers. Periodic
fires, some plants require fire for seeds to
germinate.
Temperate Grassland: Marked by seasonal drought and
fires, and grazing by large animals. Rich habitat for
agriculture, very little prairie exists in US today.
Temperate Deciduous Forest: Mid-latitudes with
moderate amounts of moisture, distinct vertical strata:
trees, understory shrubs, herbaceous sub-stratum. Loss
of leaves in cold, many animals hibernate or migrate
then. Original forests lost from North America by logging
and clearing.
Tundra: Permafrost (Permanent frozen ground), bitter
cold, high winds and thus no trees. Has 20% of land
surface on earth.
Coniferous forest: Largest terrestial biome on
earth, old growth forests rapidly disappearing,
usually receives lots of moisture as rain or snow.
Temperature
• Temperature is
partly determined
by the amount of
solar radiation
hitting an area
• Depends on
latitude, angle of
incidence
Fig. 50.11
What causes the seasons?
We know:
- Earth has elliptical orbit
- Earth is tilted on axis (23.5o)
- Seasons are opposite in northern and
southern latitudes
What causes the seasons?
• It can NOT be the distance of the earth
from the sun since the seasons are
opposite in the northern and southern
hemispheres.
Temperature
• seasons are caused by the tilt of the earth
as it revolves about the sun
Fig. 50.12
Temperature
• Ocean circulation patterns driven by
wind, continents, and rotation of Earth
Fig. 50.13c
Water
• Warming air absorbs water and cooling
releases water, causing more rain at some
latitudes
Fig. 50.13
• Local and seasonal effects on climate.
– Bodies of water and topographic features
such as mountain ranges can affect local
climates.
– Ocean currents can influence climate in
coastal areas.
– Mountains affect rainfall greatly.
Biogeography
• Biogeography is the study of past and
present distribution of individual species.
The Science of Ecology
•
•
•
•
•
Goals for the day
Differentiate Between Ecology and
Environmentalism and Conservation Biology
Trace History of Ecological Thought
Define Ecology Scientifically
Learn the Scientific Method
Organization of Ecology
The Science of Ecology
•
•
•
•
•
Goals for the day
Differentiate Between Ecology and
Environmentalism and Conservation Biology
Trace History of Ecological Thought
Define Ecology Scientifically
Determine factors determinig species
distribution
Organization of Ecology
What is the Organization of
Ecology?
• Ranges widely from individual to biosphere
studies
• Most of ecology happens in the current time
– Proximate Explanations
• Only a few fields (e.g., evolutionary ecology and
paleoecology) are concerned with past
environments and historical time
– Ultimate Explanations
Proximate Fields
• Emphasis of this course
• Examples, by scale
– Population
• Growth rates, PVA, Population genetics, Metapopulation
analyses, etc.
– Community
• Interspecific interactions, Environmental impact statements, etc.
– Ecosystem
• Energy, Matter, Nutrient flow, Pollution,
Ultimate Fields
• Evolutionary Ecology
– Using trees of relationship (phylogenies) to address
ecological questions
– E.g., evolution of swordtail length and preference in
platys
• Behavioral Ecology
– Comparing a few closely related species to address
ecological questions
• Paleoecology
– Attempting to recreate the ecology of ancient times
– One of the goals is to recreate the ancient environment in
which the lineages may have evolved
Proximate Fields Revisited
• Trends down pyramid:
– Increase in geographic scale
Population
– From single species to multiple
species
Community
– Increasing number of ecological
factors that may be influential
Ecosystem
– Decreasing certainty in results
Organismal ecology
• Questions center on how organisms
respond to biotic and abiotic factors in
their environment
• Physiology, morphology, and behavior
Population ecology
• a population is a group of organisms of the same species living in the
same place at the same time.
• questions are related to factors that affect the number of
individuals living in a habitat
– size, distribution of population?
- birth and death rates?
- population growth rate?
Community ecology
• a community consists of the organisms
that live in an area and interact
• questions focus on
– the interactions between organisms (who eats
who, who helps who)
– how those interactions affect community
structure
Competition
Mutualism
Species
Interactions
Predators and parasites
Community structure
• What factors affect community structure?
• Factors: abiotic (e.g., climate, dist.)and biotic (species
interactions)
• Community structure: species composition, number,
abundance
California serpentine grassland and adjacent oak savannah
Ecosystem ecology
• an ecosystem consists of the biotic (living)
community and the abiotic (nonliving)
factors that affect it.
• abiotic factors are things such as soil,
atmosphere, water, nutrients, energy,
temperature
• questions emphasize energy flow and
cycling of nutrients
Soil nitrogen cycle
N-fixation
N2
litter
decomp.
Bacteria
and fungi
denitrification
uptake
-
NO3
mineralization
NH4+
nitrification
leaching
Global ecology
Atmospheric CO2 and Temp.
Controls and patterns of worldwide
circulation of energy and nutrients
Global Net Primary Productivity
Fig. 54.4
2. What factors affect the
distribution of organisms?
• species dispersal
• behavior and habitat selection
• other organisms such as predators,
competitors, or facilitators
• abiotic factors such as nutrient availability,
water, temperature
(see also the rest of this powerpoint)
Focus on:
• What are the differences between different levels of ecology?
• Read about factors determining climate (average temp, average
moisture, seasons, mountain and ocean effects), but you don’t
need to know the specifics.
• For the six terrestrial biomes described, understand how temp
and moisture interact to determine the dominant species types
and levels of productivity, but you don’t need to know all the
details of each biome.
• What are the two main factors affecting types of aquatic
habitats? How do they influence light and oxygen availability?
What areas are the “tropical forests” and “deserts” of aquatic
habitats? Why?
• How do history, species interactions, and the abiotic
environment affect the biogeographic patterns of species?
Ecosystem function
• Survival of organism depends on:
– Flow of energy
– Circulation of nutrients
Energy flow
• Solar energy starting point
• Photosynthesis-water and carbon dioxide transfomed in
carbohydrates
–
–
–
–
1% solar radiation reaching earth is used for photosynthesis
30% refected back into space
20% absorbed bt the atmosphere
50%absorbed by the ground, water, vegetation
Laws of thermodynamics
Governs expenditure and storage of energy
• First law- no energy can be created nor destoryed, but can be
transformed from one form to another e.g solar energy to chemical
energy
• Second law of thermodynamics
– No energy transformation process is 100% efficient
– Transfer of energy between feeding or trohic level is lost as
heat
– Loss for ecosystem as heat energy is no longer transfeable
between organisms
– Energy flow in an ecosystem involves complex process of
photosynthesis,respiration, herbivory, carnivory and
decomposition through food chains.
Primary and Secondary
production
• Gross primary production-total fixation
of energy by autotrophs in an ecosystems
via photo synthesis
• Net primary production-gross primary
production less respiration
• Energy stored at consumer level of the
ecosystem is referd as Secondary
production
Standing Crop Biomass
•Primary productivity
•Gross primary productivity
•Net primary productivity
•Biomass
•Standing crop biomass
Secondary Productivity
Primary Productivity
Movement of Energy
Food chains
• Sequence of organism in which one organism on one preceding it
• Those organism of a food chain which have the same feeding
strategy such as primary consumers form trophic level or feeding
level
– Trophic level is determined by the number of energy steps which
precedes it i.e first trophic level belong to primary producers,
the second to primary consumers, third to secondry consumers
• Several food chains may be interconnected at different
trophic levels resulting in complex food webs
Food Chains
Foodwebs
Food chains are limited to four or five links
- energetic hypothesis: only 10% of the energy stored in organic
matter is converted to the next trophic level
• Several food chains may be interconnected at different levels
resulting in complex FOOD WEBS
Foodwebs
Ecological efficiencies
• Each step in the food chain, a considerable amount of
energy is lost fro the system
• Energy loss between trophic levels is dicteted by
second law of thermo dynamics-due to inefficient
transfer of organic matter, urinary and faecal lossses
• Energy transfer efficieny / ecological efficiencyefficiency with which energy is passed through various
steps in the trophic structure of an ecosystem
Pyramids
• Pyramids of energy are constructed by summing all the energy
transefferd between trophic levels
• Pyramds of numbers –summing number of all organisms
Inverted pyramids
• Pyramids of biomass and numbers my be inverted
– E.g a single tree represent a single organism
at the producer level and yet it supports
thousands of consumer organisms
• Ecological pyramids-result of efficiency, with which energy is
transferred from one trophic level to the next
Ecological efficiencies
• Energy transfer efficieny=(amount of
energy captured within one level of the
system or food chain)/(amount of energy
in the preceing level)
or simply
It is the ratio of energy output to energy
input
Ecological pyramids
Consider
C4
Consumer 4
C3
Consumer 3
C2
Consumer 2
C1
Consumer 1
P1
Primary Producer
Pyramids of numbers, biomass, energy!
Ecological efficiencies
• Efficiency value can be calculated for each energy transfer
process:
Harvest /Consumption efficiency
• Proportion of available energy consumed at a trophic level
• Percentage of NPPy which is eaten by herbivores
Consumption efficiency- how much pf NPP is consumed by a
specified herbivore
Herbivores capture 20-50% of NPPy because:
• 60-90% of NPP captured below ground to support root systems
• Harvester termites and other invertebrates
– Harvest upto 20%
• 20% senesces, dies and decomposes
Ecological efficiencies
(Energy content of consumed) herbage/(energy value of
NPP)X100%
• CE-affected by
–
proportion of NPP above ground factor affecting voluntatry feed intake, animal
density, length of time in which an area is utilised by animals, animal species mix
and vegetattion type
• Secondary consumers-percentage of production eaten by
carnivores
Ecological efficiencies
Assimilation or digestive efficiency
• Percenatge of food energy ingetsed by an organism that is
absorbed across the gut
– Remainder mainly undisgested is lost as faeces and enter the
decomposer compartment
• Assimilation efficiency- 20-50% herbivores, 80% carnivores????
• Plant parts assimilated diferrently
– Seeds and fruits-60-70%, leaves 50%
– Woody 15%
Trophic levels and energy
• only 10% (approx.) of energy transfers to
the next level
• e.g. 100kg grain  10g human
• but! 100kg grain  10g cow  1g human
• This puts a limit on the number of trophic
levels in a food chain.
blue whale food chain:
• planktonic algae  krill  blue whale
A pyramid of energy: note that only 10%, approx., transfers
to the next level. This imposes a limit on the number of
possible levels… usually about 4 levels.
Ecological Efficiency
Biological magnification of
DDT in the food chain (54.16)
Non-lethal doses of
pesticides, if not excreted,
can be magnified as
they are passed through
the food chain
DDT is an example!
Ecological Efficiency
100 * 6 / 67 = 9%
100 * 67 / 1478 = 4.5%
100 * 3,368 / 20,810 = 17%
Environmental concerns: land
• soil erosion and “desertification”
• land spoilage due to wars (Vietnam: >2
million hectares of rainforest; ½ Vietnam’s
mangroves destroyed)
• tropical rainforests: slash and burn
agriculture
– to turn it into a beefburger!
• loss of biodiversity
• waste disposal
Sewage
• Coliform bacteria
– presence of E. coli, which is usually harmless but
may indicate presence of other faecal
contamination
• B.O.D.
• Treatment
– Aeration, sedimentation, filtration
• Primary: sedimentation: reduces BOD by 25%
• Secondary: special filters and activation of sludge.
Removes 70% of BOD
• Tertiary: removal of phosphates and nitrates.
Lower BOD.
Air pollution
• smog: acid rain; ozone layer: global warming
• smoke: source: combustion of fossil fuels domestic and industrial
• sulphur dioxide: combustion of oil and coal,
smelting
• hydrocarbons (car exhausts)
• carbon monoxide
• nitrogen oxides
• lead (petrol)
• Lichens indicate air pollution levels
Environmental concerns: water
• surface water pollution
• groundwater pollution: aquifers
• ocean pollution
Next Week: The Tour of the
Basic Fields of Ecology Begins
• Population ecology
– Next week’s emphasis
• Community ecology
• Ecosystem ecology
• Conservation Issues
– Application of above
to real world problems