Download The Science of Ecology

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
Define Ecology Scientifically
Determine factors determing species
distribution
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
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?
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.
Types of ecosystems
• Terrestrial (land)
• Aquatic (water)
– lotic -rivers, running waters
– lentic-standing waters, lakes and resoivoirs
• Lentic ecosystems
– Great African lakes-centres of fish
biodiversity
• Lakes show thermal stratification
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
Aquatic biomes
Aquatic biomes cover about 75% of the earth’s surface
- Wetlands
- Lakes
- Rivers, streams
- Intertidal zones
- Oceanic pelagic biome
- Coral reefs
- Benthos
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
Lentic ecosystems
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.
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Factors Influencing Organismal
Distribution and Abundance
• Abiotic
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Climate
Topography
Latitude
Altitude
• Biotic
– Intraspecific Interactions
– Interspecific Interactions
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
• 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?
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
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,
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
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
Global ecology
Atmospheric CO2 and Temp.
Controls and patterns of worldwide
circulation of energy and nutrients
Global Net Primary Productivity
Fig. 54.4
Higgins, S. I. & Scheiter, S. Atmospheric CO2 forces abrupt
vegetation shifts locally, but not globally. Nature
(2012).doi:10.1038/nature11238
A new study in Nature finds that elevated CO2 concentrations
should favor trees and woody plants over savannah and
grasslands in Africa.
trees use the C3 photosynthetic pathway, which is favored under
high CO2 concentrations, whereas most tropical grasses use the
C4 photosynthetic pathways
Temperature also influences tree versus grass ecosystems, with
higher temperatures primarily selecting for the C4 grasses
Pre-industrial deforestation still warming atmosphere
Julia Pongratz and Ken Caldeira. Attribution of atmospheric CO2
and temperature increases to regions: importance of preindustrial
land use change. Environmental Research Letters. 2012. 7 034001.
doi:10.1088/1748-9326/7/3/034001.
Fossil fuels were not burned in massive quantities prior to the
Industrial Revolution, but humans were still pumping carbon into the
atmosphere due to land use change, especially deforestation
decaying vegetation, such as stumps and roots, will seep their
carbon into the atmosphere over much long periods of time,
sometimes centuries. In addition, carbon has the capacity to stay
in the atmosphere for several centuries before being absorbed by
the ocean or forests
Ecosystem function
• Survival of organism depends on:
– Flow of energy
– Circulation of nutrients
Energy flow
• Solar energy starting point
• Photosynthesis-water and carbon dioxide transformed in
carbohydrates
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1% solar radiation reaching earth is used for photosynthesis
30% reflected back into space
20% absorbed by 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 referred as Secondary
production
Primary Productivity
Food chains
• Sequence of organism in which one organism feeds 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
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
Foodwebs
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
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 efficiencies
• Energy transfer efficieny=(amount of
energy captured within one level of the
system or food chain)/(amount of energy
in the preceding level)
or simply
It is the ratio of energy output to energy
input
Ecological Efficiency
100 * 6 / 67 = 9%
100 * 67 / 1478 = 4.5%
100 * 3,368 / 20,810 = 17%