ecology. what is ecology? = “the environment” abiotic –
TRANSCRIPT
Subatomic particle
• protons• electrons• neutrons• tachyons• baryons• mesons• etc.
Subatomic Particles
Molecule C
H
H COOH
NH2 OH
H H
OCH2OPOPOP
HO
N
NN
N
NH2
HO
O O OH H
OH OH OH
H2O
N2
O2
Cl2
Subatomic Particles
atoms
Molecules
Organelle
• Sacs or their compartments that separate different activities inside the dell
Subatomic Particles
atoms
Molecules
Organelle
Cell
• (smallest living unit) May live independently or part of a multicellular organism
Subatomic Particles
atoms
Molecules
Organelle
Cell
Tissue
• A group of cells and surrounding substances functioning together in a specialized activity.
Subatomic Particles
Atoms
Molecules
Organelle
Cell
Tissue
Organ
• A group of tissues working together to perform a common task.
Subatomic Particles
Atoms
Molecules
Organelle
Cell
Tissue
Organ
Organ system
• Two or more organs interacting to contribute to the survival of the whole organism.
Subatomic Particles
Atoms
Molecules
Organelle
Cell
Tissue
Organ
Organ System
multicellular organism
• An individual composed of specialized interdependent cells arrayed in tissues, organs, and often organ systems
Subatomic Particles
Atoms
Molecules
Organelle
Cell
Tissue
Organ
Organ System
Multicellular Organism
Population: • A group of individuals of the…
Subatomic Particles
Atoms
Molecules
Organelle
Tissue
Organ
Organ System
Multicellular Organism
Cell
Population
Community
• = a group of organisms of different species (i.e. many populations)….
Subatomic Particles
Atoms
Molecules
Organelle
Tissue
Organ
Organ System
Multicellular Organism
Cell
Population
Community
Ecosystem
• All biotic and abiotic components of a certain area
Organ System
Multicellular Organism
Subatomic Particles
Atoms
Molecules
Organelle
Tissue
Organ
Cell
Population
Community
Ecosystem
Biome
• Major types of ecosystems on earth, occupying large geographic regions
Organ System
Multicellular Organism
Subatomic Particles
Atoms
Molecules
Organelle
Tissue
Organ
Cell
Population
Community
Ecosystem
Biome
Biosphere
• Those regions of the earth’s waters, crust and atmosphere in which organism can exist.
Organ System
Multicellular Organism
Subatomic Particles
Atoms
Molecules
Organelle
Tissue
Organ
Cell
Population
Community
Ecosystem
Biome
Biosphere
Factors affecting distribution of organisms (biogeography)
1. Dispersal limitations– Not all areas are accessible – geographic
isolation
2. Habitat selection• Animals
3. Biotic Factors
4. Abiotic Factors
Competition
• Whenever the quantity of useful matter or energy falls below the level needed for the maximal growth of two or more organisms which must draw on the same supply, a contest begins.
• Competition from introduced species can shrink an organism’s actual range
4. Abiotic Factors
• Vary from place to place, season to season.• Each organism has an optimum environment
needed for maximum growth.
……Thus scientists predict that global warming may radically alter the distribution of organisms/ecosystems on earth
Effects of climate on biogeography
• Solar radiation creates wind currents, ocean currents, and precipitation (from evaporation
Effects of climate on biogeography, continued
• Local climate– .– .– .– S slope drier than N slope (thus different plant
communities)• Microclimate
– .– Under a log– Within the litter layer
• Locations of the earth’s biomes due to:1. .2. .
• One biome type may occur in different areas of the world
– Different plant species but same:– Physiognomic structure –
– Similarities due to convergent evolution – similar phenotypes due to similar selection pressures over time• Similar climate, soils, disturbance patterns,…
4 types of ecological investigation:
1. Organismal ecology• “plant autecology”• organism’s response to environment – ability to
exist/adapt2. Population ecology
• Population size, distribution3. Community ecology
• Community structure, organization• Competition• Diversity• Disturbance• Succession
Characteristics of Populations
1. Dispersion –
2. Size –
3. Density - the number of individuals living in a specified area
1. Dispersion
• Patterns of Dispersion:– Clumped –
– Uniform – evenly spaced due to:• Competition for resources• Allelopathy –
– Random – unpredictable; position of one individual cannot be predicted from position of another.
2. Population Size
• Demography = study of factors that affect the growth & decline of populations
• Life Histories = events from birth through reproduction to death
– Trade-offs between investments in reproduction & survival when there are limited resources
Controls at every stage of life history
Dormancy (seed bank)
seedling
growth
mature plant
reproduction
death
Seeds washed away, eaten, decomposed
Seed rain from mature plants
Herbivory, disease, competition, drought, flood, freeze
Exponential Growth
• occurs when resources are abundant or when an important constraint has be removed.
• Ex.
Biotic Potential (r)
• = Intrinsic/ maximum rate of natural increase, given:
• Habitat is free of predators and pathogens.
Limits on Population Growth
• Given their biotic potential what keeps organisms from filling up the planet?
Limits on Population Growth
• Density & competition for resources will cause reproduction rates to decline or stabilize
Any essential resource that is in short supply
is a limiting factor on population growth.
• living space• pollution-free environment
• Environmental resistance affects the number of individuals of a given species that can be sustained indefinitely in a particular area.
Time
Number of
Individuals
K
Introduction
Colonization
Naturalization
Carrying Capacity (K)
• =
• Is not fixed - K may decrease when a large population damages or depletes its own resource supply.
3. Density-Dependent Control of Population Size
• When population density is low, a population grows rapidly.
• When density is high, populations may grow slowly, remain stabile (zero growth) or decline – why?.
• High density puts plants at greater risk of …..
Density-Independent Control of Population Size
• = events that cause more deaths or fewer births regardless of population density
• Examples?
Plants have developed adaptations to population density
• At low density, population is limited only by intrinsic rate of growth (r)
• At high density, population is limited by carrying capacity (K)
• R selection and K selection
r - selection
• Disturbance creates low-density conditions, frees resources (fire, flood, volcano)
• Biotic potential (r) limits population size• Adaptations that are successful for these
conditions:
K-selection
• High density, population size close to K• Not much “new” space – competition for
resources• Adaptations that are successful for these
conditions:
• K & r selected species exist together because small-scale disturbances create space (exposed soil) for r species (colonizers)– Ex. Downed tree, badger holes, grazing
disturbance
Review: definition of community
• Group of organisms of different species living together in a particular habitat
Characteristics of communities
• Diversity – composed of:
1. Richness –
2. Evenness –
• Relative abundance = # individuals of species X divided by total # of individuals in the community
What factors determine the plant species composition & the relative of abundance of
different species in a community?
• Biotic & abiotic components of the habitat
Abiotic components of habitat & their effect on community structure:
• Each species has a tolerance range –
• Climate – temp, moisture• Soil – types, pH• Latitude & altitude• Disturbance
Disturbance
• = decrease or total elimination of the biotic components of the habitat
• Results: decrease in biomass, diversity• Natural events –
• Human-caused –
• Frees resources, creating opportunities for new species, different composition
• All communities have evolved with some type of disturbance, varying in type, frequency, & severity
Small-scale, frequent disturbance
• Ex. Trees downed in wind storm
• Can prevent large-scale disturbance – fire!– Ex. Yellowstone fire of 1988– Fire suppression in fire-dependent ecosystem
caused massive, stand-replacing fire
Human - caused disturbance + introduced species = disaster
• Ex. Cheatgrass – wildfire cycle1. Overgrazing in ecosystem that did not evolve
with large herbivores2. Cheatgrass introduction3. Decrease in fire frequency (100 yr to 5 year
cycle)4. Conversion of ecosystem with tremendous loss
of diversity• These types of problems creating mass extinction
worldwide
Biotic components of habitat & their effect on community structure
1. The plant itself
• Benefit ex: beech/oak forest creates shade needed for other young beech & oak to grow
• Detriment ex: pine forest creates shade but pines need lots of light to grow (succession)
2. Other plant species
• Theory of competitive exclusion: when two species compete for the same limiting resource (occupy the same niche), the species that is less adapted will be excluded from the community by the superior competitor
• One will become extinct or evolve to use a slightly different set of resources
low highLight intensity
Spe
cies
Abu
ndan
ce Species A Species B
A B C D
• If this theory is true, then actually very little competition in nature, because each plant occupies a niche.
• Niche• =
• Includes all aspects of a species’ use of biotic & abiotic resources (microclimate, rooting zone, pollinators, etc)
3. Other (non-plant species)
• Interactions with animals, insects, fungi, bacteria• Mutualism –
– Ex.
– Ex. Pollinator gets nectar and plant gets pollen transfer
– Ex. Animals eat fruit (nutrition) and seeds are dispersed
– Ex. Acacia trees get defense from herbivores & ants get home, food
• Commensalism – one species benefits & other is not affected
• Competition –
• Predation – one harmed, other benefits– Herbivory– pathogens
Controls on community structure
• Dominant species = species with the highest abundance or biomass in the community
– Controls occurrence & distribution of other species
– If eliminated, other species take over– Ex. Douglas fir
• Keystone species
– Ex. Sea otter – reduction in populations caused boom in sea urchin population, destroying kelp forests (drastic decline in diversity)
Succession
• =
• Species replacement continues until the composition of species becomes relatively steady under prevailing climatic conditions & disturbance regimes (dynamic equilibrium, not climax).
1. Primary succession
• Sequence:
1..
2.As these decay, acids weather the rock & primitive soil forms
3.Pioneer plants establish (r-selected)
4.Pioneers replaced by K-selected species
The Nature of Pioneer Species
• typically small plants, short life cycles, producing an abundance of small seeds which are quickly dispersed (wind & water)
• can grow in N-poor soil because of their mutualistic interactions with nitrogen-fixing bacteria.
What Pioneers Do: Facilitation
• accumulation of their wastes and remains adds volume to the soil and enriches it with nutrients that allow other species to take hold.
2. Secondary Succession
• Plant community is destroyed but soil remains/ new soil exposed
• Examples?
• Typical progression: small herbs & grasses shrubs trees
Pioneer species
• Sometimes these opportunistic species (especially invasive weeds!) inhibit the growth of the native climax species changing the structure and type of climax community forever.
• Ex. cheatgrass
Structure of Ecosystems
1. Physiognomic structure • =
• Relative abundance of trees, shrubs, herbs, mosses, etc.
• Phenotypes, physical characteristics• Vertical & horizontal stratification
3. Species composition
• Determined by soil resources, climate tolerance ranges, stresses (ex. Competitive interactions, herbivory)
4. Trophic levels
• = Feeding levels• Autotrophs
– First level of all food webs---- primary producers
• Heterotrophs – consumers - depend directly or indirectly on energy stored in tissues of primary producers.
Types of Heterotrophs• Herbivores
• Parasites
• Detritivores
• Carnivores – eat herbivores & other carnivores – secondary consumers
• Omnivores partake of a variety of edibles• Decomposers - extract energy and recycle nutrients from
organic matter.
• Some organisms like man extract energy from more than one trophic level so it is hard to assign them to a specific trophic level.
• Actual feeding relationships in an ecosystem are complex –.
Primary Production
• =
• How much energy actually get stored depends on:• 1) how many plants are present and • 2) the balance between photosynthesis and aerobic
respiration.• Ecosystems differ in their PP:
• Other organisms tap into the energy that is conserved in plant tissues, remains, or wastes.
• They, too, lose heat to the environment.
Secondary Production
• =
• Ex. Caterpillar eating a plant:– 50% loss to feces (energy transfer to detritus)– 34% to respiration (heat loss)– 16% to growth
Trophic efficiency
• =
• Thus 85-90% of available energy at one level is not transferred to the next– Instead lost as heat, not consumed, or
transferred to detritus