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.
LAKE EUTROPHICATION
High levels of P
and N containing
compounds
(fertilizers/
detergents)
Low oxygen = other
organisms die out
Algal Bloom
Algae die = food
for decomposers =
population grows
Decomposers break down material
and use up oxygen in lake
•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
10
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.
The Hydrologic Cycle
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
1.3b) Ecosystem
Structure
Trophic level = category of
organisms defined by how they
get energy.
• 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
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
1.3c) Trophic Levels in Ecosystems
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.
Count trophic
levels as steps
from the
original
energy source
Food chain movie
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
Trophic
Levels
Food Chain - simplistic
Food chain
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 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 levels
2. 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
a)Pyramid of numbers
- # of organisms at each trophic level
- each bar represents
numbers relative
- pyramids are
to the pyramid base
based on data
from a given area
eg: 1 km 2
tertiary consumer
secondary consumer
Primary consumer
Producer
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 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 flow not,
Energy cycling
Energy lost
as heat
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.
DDT interfered with
Calcium deposition
Soluble in water,
Collects in fatty tissue
Human use of
Pesticides
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
Increased soil =
shallow rooted
trees (pine)
Soil formation
(lichens die/
break up rock)
Pioneer community
(lichens, mosses)
Grasses die = more
soil = shrubs and
weeds take over
Increased pine = more shade =
favorable for deeply rooted plant
(maple/ birch)
Enough soil =
grasses out compete
lichens
Climax Community
*Climax community is the stable
community that results.
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.
2.
3.
4.
•
Number of births (natality).
Number of deaths (mortality).
Immigration (movement in).
Emigration (movement out).
Density
independent
Density
dependent
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.
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 Adaptations
adaptation:
•
•
•
accumulation of traits which improve a species ability to survive.
mechanism is natural selection
Evolution: Library: Evolution of
better-suited traits to environment are passed on.
the Eye
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
pitcher plant
c) Behavioral
•
•
actions
Examples: migration, hibernation
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
Evolution: Library: Sweaty T-Shirts and
Competition
Human Mate Choice
Variation
Survival of the fittest (cartoon)
Origin of new species by inheritance of
successful variations.
Evolution: Survival
2) 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.
The Peppered Moth
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:
Evolution: Sex: The Mating Game
- 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.
Darwin:
• originally, most giraffes had short necks, but
some variation existed.
• as food supply on lower branches dwindled,
short-necked giraffes did not survive; longnecked 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.