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
Is Life uniformly distributed? Is life uniformly distributed?
Why isn’t all life everywhere?
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
3. Biotic Factors Absence of symbioses Lack of pollinators 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
What do plants compete for?
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
Fig Your ecosystem type: coastal temperate rainforest
Locations of the earth’s biomes due to: 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,…
1. Tropical rainforest Very diverse! Large vertical stratification due to competition for light
2. Savanna Rainy & dry season Fire adapted
3. Desert CAM plants Unique plants with adaptations to harsh environment
7. Coniferous Forest 4 seasons, large amounts of snowfall
8. Tundra No trees or tall plants 20% of land area on earth Low annual precipitation
4 types of ecological investigation: 1.Organismal ecology “plant autecology” organism’s response to environment – ability to exist/adapt 2.Population ecology Population size, distribution 3.Community ecology Community structure, organization Competition Diversity Disturbance Succession
4. Ecosystem ecology Energy flow/nutrient cycling Interactions of biotic & abiotic components
Plant Population Ecology
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.
Uniform dispersal of sagebrush
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
Demography Change in Population size = (B + I) – (D + E)
Exponential Growth occurs when resources are abundant or when an important constraint has be removed. Ex.
The j-shaped curve Time Number of Individuals
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.
Time Number of Individuals Initial carrying capacity New carrying capacity Logistic growth
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
Pop. Size Time Low density High density introduction Colonization Naturalization
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
Plant Community Ecology
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
Which community is more diverse?
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
= 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 cycle 1.Overgrazing in ecosystem that did not evolve with large herbivores 2.Cheatgrass introduction 3.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 high Light intensity Species Abundance Species A Species B A B C D
A BCD Species A Species B
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).
Two major types of succession Primary Succession Secondary Succession
1. Primary succession Sequence: 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.
Example of primary succession: glacial retreat
. Mosses, lichens, fireweed Dryas stage
Alders & cottonwoods dominate
Spruce enter forest and replace alders/cottonwoods
Hemlock slowly replace Spruce. Hemlock is “climax”
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
Ecosystems An ecosystem is an association of organisms and their physical environment,
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.
Decomposition links all trophic levels Fig 54.2
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 –.
Energy Flow Through Ecosystems
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.
All of these heat losses represent a one-way flow of energy out of the ecosystem.
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