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Unit D: Changes in Living Systems
Science 20: Chapter 1
The Biosphere of Life
1.1) Biosphere• The narrow zone around the earth where
life exists.
• Biosphere consists of 3 components:– Lithosphere, Hydrosphere and Atmosphere.
• Biotic = living organisms (life forms).
• Abiotic = nonliving component (geological and physical factors).
• Ecological studies investigate a specific environment by looking at the following:
1.Organism (the individual).
2. Population (group of individuals).
3.Community (1 or more populations).
4.Ecosystem (community and abiotic factors interact).
* Example: Prairie ecosystem; who’s who?
1.1b) Habitat• Water is the most important abiotic factor
of an ecosystem.
• The habitat of an organism determines the amount of water, sunlight and temperature for growth and survival.
• Habitat = abiotic and biotic factors that encourage survival.
• What is your ideal habitat? Why?
1.1c) Nutrients
• Nutrients are needed compounds/elements used by organisms to grow and reproduce.
• Gardeners use fertilizers to give all the needed nutrients to the plants.
• The run-off from fertilizers can cause problems with lakes and algal blooms.
Fertilizers
fertilizer - chemicals that contain nitrogen and phosphorus natural fertilizer
Manure: contains N which is ammonified first in the soil, then nitrified to provide useful nitrates
Commercial Fertilizers: 3 numbers:• The first number is the % nitrogen (by weight)• The second number is the % phosphorus (by
weight)• The third number is the % potassium (by weight).
• pollution increases the natural eutrophication process of water. Why?• Unnatural Eutrophication: a process in which nutrient runoff from
agricultural lands or livestock operations causes photosynthetic organisms in ponds and lakes to multiply rapidly
• Human-caused eutrophication wiped out fisheries in Lake Erie in the 1950s and 1960s.
• algal blooms are harmful rapid growth of algae, causing eutrophication.
10
High levels of P and N containing compounds (fertilizers/ detergents)
High levels of P and N containing compounds (fertilizers/ detergents)
Algal BloomAlgal Bloom
LAKE EUTROPHICATIONLAKE EUTROPHICATION
Algae die = food for decomposers = population grows
Algae die = food for decomposers = population grows
Decomposers break down material and use up oxygen in lakeDecomposers break down material and use up oxygen in lake
Low oxygen = other organisms die outLow oxygen = other organisms die out
•Water in which oxygen becomes too low to support animal life is called eutrophic.
•To protect Canadian lakes, ponds, and streams from becoming eutrophic, some states no longer allow the sale of detergents containing phosphorus compounds.
Classification of lakes by the nutrient input which also determines the primary producers.
Oligotrophic lake: Nutrient-poor, photosynthesis-limited, clear water, O2 rich.Eutrophic lake: Nutrient-rich, high photosynthesis, murky water, O2 poor.
1.1e) Hydrological cycle
• Water plays a critical role by:– Maintaining global heat balance.– Acting as a solvent in reactions.
• Movement of water through environment: from atmosphere to earth.
• Volume of water remains constant, specific amounts vary in phases; water continuously cycles.
1.2) Biotic factors
• Ecology = study of the interactions of living organisms with their environment and each other.
• Biomass = dry mass of all organisms in an environment.
1.2b) Symbiosis• Symbiosis = “living together”
– Long lasting relationship that benefits at least 1 organism of 2 different species
• Types of symbiosis:– Mutualism: both species benefit.– Commensalism: 1 organism benefits, the other
is unaffected/unharmed.– Parasitism: 1 organism (parasite) benefits by
harming the other (host).
See page 417 and identify the relationships!
1.2c) Predator-Prey Interactions
• This is NOT symbiosis; the 2 organisms do not live together and it is a short interaction.
• Predation: 1 organism(predator) kills the other (prey).– Mostly benefits the predator BUT the prey
community is left with fit individuals.
What type of relationship is this?
1.2d) Competition
• Competition is where 2 or more organisms compete for the same resource.
• All organisms involved are harmed; no one benefits.
• This is NOT symbiosis.
Assignment
• Please complete the following:– Read and highlight the important points on
“biomes and habitats” and “animal partnerships”.
– Complete #2,3 and 4 on page 412.– Complete the Symbiosis Fact sheet.– Complete #2,3,5 on page 422.
1.3) The web of life
•Matter and energy are essential components of the universe and living organisms.•Matter - everything that takes up space and has mass•Energy - the capacity to do work
•the biosphere is composed of a variety of ecosystems•each ecosystem has a structure based on
a) energy flows
b) matter cycles
• An ecosystem = all the organisms living in a community and all the abiotic factors they interact with.
1) Autotroph (producers) • organisms that:
1. get energy from sunlight or inorganic energy sources.
2. convert inorganic compounds to organic forms.
3. are the basic trophic level in an ecosystem; supports all other organisms
1.3b) Ecosystem Structure
Trophic level = category of organisms defined by how they get energy.
2)Heterotroph (consumers) : organisms that derive their energy by consuming other organisms.
a) Primary Consumers
- herbivores (eat only plants)
b) Secondary and Tertiary Consumers
- carnivores (eat other animals)- omnivores (animals which eat both producers and
consumers)
3)Decomposers
- organisms that derive their energy from dead organisms and waste products.
1. scavengers (eat tissues from dead organisms).
2. Decomposers (breaks down complex molecules into simple sugars)
Why is decomposition important?
recycles organic material into inorganic
Trophic levels
• the steps in the transfer of energy and matter within a community (feeding levels)
• species in an ecosystem are divided into trophic levels on the basis of their main source of nutrition.
• three main types of trophic levels are producers, consumers, and decomposers.
1.3c) Trophic Levels in Ecosystems
Count trophic levels as steps from the original energy source
1.3d) Food Chains• organization of
trophic levels where energy flows from producer to primary and secondary consumers (and others if present)
• Simple feeding sequence: who eats who
• Not representative of complex ecological relationships
TrophicLevels
Food chain movie
1.3e) Food Webs• interconnected food chains within an ecosystem
•highlight the complex, real-world interactions between species
• makes connections from primary producers, through consumers, and back to decomposers
Food Chain Movie
Food Web - complex
Interactions in an aquatic food webInteractions in an aquatic food web
IV. Ecological Pyramids
1.3f) Ecological Pyramids• Because of the loss of energy with trophic levels, there are two
consequences for the ecosystem: 1. Because productivity is lower at higher trophic levels, there is less
biomass at these levels2. Lower biomass at higher trophic levels, combined with large body
size of top consumers, results in lower population densities
•Most stable ecosystems have complex and well developed food webs the removal of one of its organisms may have little effect
• results in a stepwise decrease in energy (pyramid)
• there are 3 types of pyramids in common use by ecologists
Producer
Primary consumer
secondary consumer
tertiary consumer
a)Pyramid of numbers - # of organisms at each trophic level- each bar represents numbers relative to the pyramid base - pyramids are
based on data from a given area eg: 1 km 2
b) Pyramid of Energy - energy stored by each trophic level is given in calories
or Joules. Energy per unit area per unit time (Kcal/m2/yr).
Efficiency of energy transferEfficiency of energy transfer::
c)Pyramid of Biomass – stored energy is represented by biomass (dry
weight) Biomass per unit area per unit time (g/m2/yr)
•Energy is lost at each step in a food chain or web; the general estimate of this loss at each step is 90%, so only 10% of energy consumed is available to the next trophic level. This is known as the 10% rule.
Energy Loss –
Energy lost as heat
Energy flow not,Energy cycling
Could we feed a larger population of humans if we ate only plants?
Yes, since most of the energy in ecosystems is stored in the bodies of primary producers. Only about 10 percent of the energy at one energy level passes to the next highest trophic level, therefore less individuals can be fed at higher levels.
The behavior of energy is best explained by the Laws of Thermodynamics.
Where do photosynthesis and cellular respiration fit in? What are they?
Laws of Thermodynamics:
a) First Law of Thermodynamics
•Energy cannot be created or destroyed, only changed from one form to another
b) Second Law of Thermodynamics
•With each successive energy transfer, less energy is available to do work. In biological systems, this “waste” energy is often heat.
Assignment
• Please complete the following:– Practice #2 worksheet #1,4,5,8.– Investigation #2 worksheet: Complete entire lab
(#1-8, extension).
1.4) Planning Field study
• Complete the elk island field study.
1.5) Recycling of matter
• Matter is recycled, but energy is not.
• Even when trees die from a fire, their seeds do not and plant new seedlings.
• Recycling happens through biogeochemical cycles: the movement of elements/compounds between abiotic and biotic parts of the environment.
1.5a) The Carbon and Oxygen cycle• Cycling of Carbon and Oxygen.• Carbon is a component of all living and dead
organisms; considered organic.• Plants perform Photosynthesis (Carbon
dioxide --- glucose) and Animals/Plants perform Cellular respiration (Oxygen --- Carbon dioxide and energy).
• Soil organisms (bacteria) decompose dead organisms and return carbon.
• Reservoirs of carbon = carbon sinks.
carbon cycle animation
b. Fossil fuels
• Dead organisms are compressed into fossil fuels; when it is burned, it releases carbon into the atmosphere.
• Added Carbon disrupts natural cycling, leading to climate change.
• The Greenhouse effect: Carbon Dioxide traps energy in the atmosphere and increases the temperature of the earth.
c. Greenhouse effect
Greenhouse Effect - animated diagram
1.5b) Nitrogen cycle• Includes 4 Processes: Nitrogen fixation,
ammonification, nitrification and denitrification.
• Nitrogen is an important component of all proteins and nucleic acids.
• Most organisms can’t use Nitrogen directly; it must be put into soli by:– Volcanic action.– Lightening.– Nitrogen- fixing bacteria.
Nitrogen fixation and Ammonification• Nitrogen fixation: bacteria (90%)/lightening
(10%) convert atmospheric nitrogen into roots of plants (legumes).
• Fertilizers increase this amount.
• Ammonification: Decomposers convert nitrogen products (from tissues) into ammonia (NH3).
Nitrification and Denitrification
• Nitrification: process changing ammonium ions into nitrates (NO3), performed by nitrifying bacteria.
• Absorbed by plants, used to make a.a’s: absorbed by consumer when eaten.
• Denitrification: Bacteria convert ammonia into Nitrogen, which returns to atmosphere.
nitrogen cycle animation
Pesticides• Pesticides have had the largest impact on food webs
• Pesticides benefit society – reduce the number of pests (weeds, molds, insects, birds, etc.) to increase crop
production
– Reduce the spread of disease (malaria, West Nile)
• Pesticides have also negatively affected ecosystems:
• Eliminating an insect species on small island using DDT reduced the spread of malaria, however, the entire food web of the island was affected: other insects disappeared - then lizards - then cats - increasing rat population – outbreak of disease = more problems!!!
• Biological amplification/ magnification – the buildup of toxins as you move up a food chain.
• Therefore, the higher the trophic level, the greater the concentration of toxins
• Toxins affect the environment in unexpected ways.. Example: DDT accumulation in the Peregrine Falcon creates thin shells, therefore breaking easily. The numbers of the species in Canada decreased so dramatically, that they were close to extinction.
Human use of Pesticides
Soluble in water,Collects in fatty tissue
DDT interfered withCalcium deposition
Time magazine in 1947
Assignment
• Please complete the following:– Carbon and Oxygen Cycle.– Nitrogen cycle.– Finish labeling all of the cycles!
Science 20: Unit D
Chapter 2: Changing Populations
2.1) Ecological Succession
The Process of Succession
•Describe the community in the picture on the right.
•Ecological succession is a community change in which new populations of organisms gradually replace existing ones
•Succession occurs from natural causes (competition, fire, earthquakes, etc) or due to man (logging, mining, farming etc).
Primary Succession
•Primary succession-Succession that begins in an area where there is no existing community
•Causes of prim Succession: volcanic eruption, glacier retreat
•The first group of organisms to occupy an area undergoing primary succession is called a pioneer community
•Pioneer organisms must be hardy and able to live on minimal resources
•Lichens are pioneer organisms; humus is the organic component of soil created from decomposing organisms.
Primary Succession Animation
Steps in Primary Succession:
Glacier Retreats exposing Parent rock Glacier Retreats exposing Parent rock
Pioneer community (lichens, mosses)Pioneer community (lichens, mosses)
Soil formation (lichens die/ break up rock)
Soil formation (lichens die/ break up rock)
Enough soil = grasses out compete lichens
Enough soil = grasses out compete lichens
Grasses die = more soil = shrubs and weeds take over
Grasses die = more soil = shrubs and weeds take over
Increased soil = shallow rooted trees (pine)
Increased soil = shallow rooted trees (pine)
Increased pine = more shade = favorable for deeply rooted plant (maple/ birch)
Increased pine = more shade = favorable for deeply rooted plant (maple/ birch)
Climax CommunityClimax Community
*Climax community is the stable community that results.
Primary Succession:Primary Succession:
Primary Succession Animation
2.1b) Aquatic Succession• Occurs when water collects in a basin; algae
starts to grow; eggs are planted in water; fish hatch and attract birds to the water.
• Nutrients from runoff create soil for plants to grow; plants grow on edge (cattails).
• When lots of plants overtake water = terrestrial ecosystem.
2.2) Secondary Succession
•Secondary succession: occurs in an area where an existing community has been partially destroyed
•Examples: Fires, logging, farming
•Occurs more rapidly then primary succession
•A community that achieves relative stability is called a climax community.
•Climax communities tend to have greater species diversity than the communities that precede them.
Why are there prescribed burns? Is this a good thing?
Assignment
• Please complete the following:– Environmental changes and succession
worksheet (omit #1 and 2).– Sketch the process of primary and secondary
succession, with labels, in your duo tang!
2.3) Populations
• Populations can grow so fast that they exhaust their resources. Examples?
• Why is this a problem? Where do we see this happening today?
• In order to study population growth, bacteria is used; it is easy to study and can imitate human populations very well.
2.3b) Exponential Growth
• The rapid growth in population caused by constant increase.
• Growth rate is measured using doubling time- the time it takes for the population to double.
• Exponential Curve (J curve): when data is graphed, the shape is a J. The population is increasing and growing exponentially.
2.3c) Factors that affect populations
• 4 major factors:1. Number of births (natality).
2. Number of deaths (mortality).
3. Immigration (movement in).
4. Emigration (movement out).
• 2 types of populations:1. Closed: No movement in/out due to natural/artificial
settings. Only death/births affect population.
2. Open: exist in natural setting where all 4 factors affect population size.
Density independent
Density dependent
2.3d) Population explosions and crashes
• If an organism is introduced where there are no predators; a population explosion/growth occurs.
• What happens when the food is gone? The population crashes!
• Example: Rabbits released in Australia (1859).
• Curve shape: J curve (up and down).
2.3e) Carrying Capacity
• The maximum number of individuals that can be sustained by an ecosystem indefinitely; limited by disease, competition and famine.
• Instead of crashing, the population levels off at a stable number of organisms.
• Curve shape: S curve.
2.3f) Malthus
• Thomas Malthus was the first to hypothesize how populations grow.
• He predicted that the human population would crash because of shortage of resources. Why did this not happen?
• Do you think a population crash will occur? Why or why not?
Assignment
• Please complete the following:– Population growth curves– Population regulation
2.4) Adaptations• Snails- the perfect organism to study
because they have been around for 500 million years.
• Generations (a single step in the line of descent) can be found and the morphology (the shape and form of the organism) can be studied.
• Help to shape the fossil record (the record of all fossils on earth).
2.4b) Evolution• Means “change over time”: gradual changes
in organisms happen over generations; eventually producing new species.
• Occurs in a population, not single organisms.
• Are genetics related changes.
• 2 versions:– Gradualism (Darwin).– Punctuated equilibrium (Stephen Jay Gould).
Gradualism vs. Punctuated Equilibrium
• Gradualism:– Organisms accumulate changes gradually over
time, these slow changes eventually lead to new species.
• Punctuated Equilibrium:– A new mutation that is favorable in a population
will rapidly out compete the old genes = Sudden change!
– Between times of rapid change are long periods of little natural selection.
2.4c) Mechanism of inheritance
• Each organism has 2 sets of genes (DNA passed from parent to offspring) that determine characteristics of the organism.
• When genes are passed to offspring, they are copied and can mutate or change; this leads to variation in a species.
• Mutations can be good or bad; they increase or decrease the probability of survival.
2.4d) Types of Adaptationsadaptation: • accumulation of traits which improve a species ability to survive.• mechanism is natural selection• better-suited traits to environment are passed on.
a) Structural• modifications of shape and size to allow special functions• Examples: fingers of humans adapted to grasping/ holding; “fingers” of bat
adapted to support wing-leaves of pitcher plant
b) Physiological • development of chemicals in the organism• Examples: digestive chemicals in pitcher plant to digest insects
- venom of snakes
c) Behavioral• actions• Examples: migration, hibernation
Evolution: Library: Evolution of the Eye
pitcher plant
2.5b) Lamarck’s Theory• Believed in spontaneous generation: new
species created from non-living matter and gradually become more complex.
• Known as “Inheritance of acquired characteristics”.
• Organisms had a “force”/ “desire” that causes them to change for the better; must produce new parts to meet desire.
• Use and misuse of parts passed to offspring.
• Example: giraffes.
Darwin’s finches.Watch the slideshow of the Galapagos islands; very cool!
2.5c) Darwin’s theory
• Theory developed while on board the HMS Beagle; returned in 1836.
• Suspected the following:– Living forms descended from fossils.– Species evolve independently if isolated.– Evolution due to difference in habitat.– Geological forces responsible for location of
fossils and mountains.
Evolution: Darwin
Galapagos Islands: A unique Island Ecosystem
1) Natural Selection
• Central theory to Darwin’s evolution.• 5 distinct areas:
– Overproduction– Competition– Variation– Survival of the fittest (cartoon)
– Origin of new species by inheritance of successful variations.
Evolution: Survival
Evolution: Library: Sweaty T-Shirts and Human Mate Choice
2) Peppered Moth
The Peppered Moth
The light-colored form of the moth, known as typica, was the predominant form in England prior to the beginning of the industrial revolution. Shown at left, the typica moth's speckled wings are easy to spot against a dark background, but would be difficult to pick out against the light-colored bark of many trees common in England.
Around the middle of the 19th century, however, a new form of the moth began to appear. The first report of a dark-colored peppered moth was made in 1848. By 1895, the frequency in Manchester had reached a reported level of 98% of the moths. This dark-colored form is known as carbonaria, and (as shown at right), it is easiest to see against a light background. As you can well imagine, carbonaria would be almost invisible against a dark background, just as typica would be difficult to see against a light background. The increase in carbonaria moths was so dramatic that many naturalists made the immediate suggestion that it had to be the result of the effects of industrial activity on the local landscape.
1. Overproduction: - More offspring produced than can survive,
reproduce and live to maturity.
2. Competition: - Organisms must compete for food, water and
shelter.
3. Variation:- differences in species that are passed to offspring.
4. Natural Selection:- Individuals that are well adapted to their environment
are more able to compete, survive and reproduce
5. Inheritance of successful traits:- Over generations, new species arise through inherited
genes; a new species is produced.
Evolution: Sex: The Mating Game
Darwin:• originally, most giraffes had short necks, but
some variation existed.• as food supply on lower branches dwindled,
short-necked giraffes did not survive; long-necked giraffes did survive.
• “fitness” = measure of reproductive success.• “survival of the fittest” ---> only giraffes that
were adapted for a longer neck (genetics) fit the environment.
• long-necked giraffes were better suited to their environment, therefore more likely to survive and reproduce ----> long necked giraffes survived.
• over a long period of time, the population of giraffes changed from mostly short- necked giraffes to mostly long-necked giraffes ---->EVOLUTION.
origin of species
2.5d) Evidence for evolution
• 4 main areas:– Theory of Continental drift/Pangaea– Fossil records– Embryology– Comparative Biochemistry
• Evidence comes from direct (fossils, continental drift) or indirect (embryology, biochemistry) investigations.
1) Fossils• Fossil = remains of plants/animals preserved
in rock/tar/amber/ice.• The fossil record shows organisms once
existed on earth that don’t exist now; some bear resemblance to those that exist now.
• Recent fossils resemble present day species; older fossils are more primitive.
• Rocks are dated using radio-carbon dating.• Fossil record is not complete---- there are
“missing links”.
Observe how fossils can form.
Observe an animation of clastic sedimentary rocks forming.
2) Embryology
• Study of organisms in the early stages of development.
• Embryos of all vertebrates are remarkably similar in early stages.
• Embryologists suggest this is because all vertebrates evolve from a common ancestor. Many embryonic structures are similar to those found in ancestors.
a) Vestigial Structures
• Muscles/Appendages that are considered to be useless.
• Includes: tails, ear muscles, appendix and limb bone of whale.
• Were these once useful?
b) Homologous structures
• Have common origins in the embryo (ex. Gill slits), but may appear quite different in adults.
• Have the same structure, but different functions.
d. Biochemistry
• Analysis of DNA and proteins show that animals may have remarkably similar DNA.
• Differences arise by mutations accumulated overtime.
• The closer the “DNA fingerprint”, the more closely related the organisms are.
2.5e) Asexual reproduction
• To avoid mutations, asexual reproduction occurs in many plants. The parent clones an exact copy of itself = the daughter.
• This happens with “cuttings” of plants, cloning of cells and “runners”.
Assignment
• Please complete the following:– Homologous structures– Genes and Evolution– Mechanisms of Biological change– Chapter 2 review (odds only).• Remember that you have a unit exam on
chapters 1 and 2; do review questions from both!
• Pages 464-467; Pages 505- 509.
