Download The information in this document covers the IB syllabus for topic 5

IB Biology
Notes for Ecology & Conservation
The information in this document covers the IB syllabus for topic 5 (not 5.4) and option G. Sections
where headings have been highlighted indicate material that is only tested in HL Biology.
Introduction to Ecology
First, a few definitions:
• ecology = the study of relationships between living organisms and between organisms and their
environment
• ecosystem = a community and its abiotic environment
• population = a group of organisms of the same species who live in the same area at the same
time
• community = a group of populations living and interacting with each other in an area
• species = a group of organisms which can interbreed and produce fertile offspring
• habitat = the environment in which a species normally lives or the location of a living organism
• autotroph = an organism that synthesizes its organic molecules from simple inorganic
substances
• heterotroph = an organism that obtains organic molecules from other organisms
• consumer = an organism that ingests other organic matter that is living or recently killed
• detritivore = an organism that ingests non-living organic matter
• saprotroph = an organism that lives on or in non-living organic matter, secreting digestive
enzymes into it and absorbing the products of digestion
• trophic level = the position that an organism occupies in a food chain or a group of organisms
in a community that occupy the same position in food chains
Types of heterotroph:
•
•
•
•
•
•
herbivores are organisms that consume only plant matter
o cows, rabbits, koalas, pandas
carnivores are organisms that consume only animal flesh (and kill their food)
o lions, tigers, sharks, orcas
omnivores are organisms that consume both plant & animal matter
o humans, bears
piscivores are organisms that consume only fish
insectivores are organisms that consume only insects
sanguivores are organisms that consume only blood of other animals
Food chains
A food chain is a diagram that shows “what eats what”…basically, how organisms get their food. A
food chain is linear, and uses arrows to show the direction of energy flow up the chain.
1. grass  cow  human  mosquito
2. phytoplankton  zooplankton  herring  salmon  seal
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Food webs show the interconnections between food chains in a particular ecosystem.
http://www.twingroves.district96.k12.il.us/Wetlands/Mosquito/MosqGraphics/MosquitoFW.gif
Remember, in food chains & food webs, the arrow indicates, “is eaten by”, so in the web above, algae
is “eaten by” both smelt and mosquito larvae.
Trophic levels
You should be able to identify the trophic level of any organism in a food chain or web.
1.
2.
3.
4.
Autotrophs are the first trophic level. They are also referred to as producers.
Primary heterotrophs are the second trophic level. Heterotrophs are also called consumers.
Secondary heterotrophs are the third trophic level.
Etc.
Because of energy losses, most food chains max out with the tertiary or quaternary consumers.
Yet another definition… the biosphere is the total of all areas where living things are found; this
includes the deep ocean and the lower atmosphere.
The biosphere consists of interdependent and interrelated ecosystems. It is organized into biomes,
which are large geographical regions with similar climate, flora and fauna. Examples of biomes
include tundra, desert, tropical rainforest, boreal coniferous forest, temperate deciduous forest, and
grassland.
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Energy in Ecosystems
All energy in ecosystems originates from the Sun. Producers (photoautotrophs) convert solar (light)
energy to chemical energy (food). Energy flow is unidirectional…it is not recycled. Typically, between
10%-20% of energy is passed on from one trophic level to the next. Energy losses from one level to
the next are caused by:
• heat loss through cellular respiration
• material not consumed (e.g. bones, beaks, fur, feathers)
• material not assimilated – given off as waste
Pyramid of Energy – a diagram that represents the energy at each trophic level. Units are generally
kJm-2yr-1.
Pyramid of Biomass – a diagram that represents the amount of biomass (dry weight of organisms) at
each trophic level. Biomass gives us a rough estimate of the energy in an ecosystem, since all the
molecules in organisms are essentially the same and in the same proportions.
Pyramid of Numbers – a diagram that represents the number of organisms at each trophic level. It may
be inverted, if, for example, the ecosystem is a single tree supporting many heterotrophs.
All images from http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/F/FoodChains.html
Matter in Ecosystems
All matter in ecosystems is recycled. Decomposers and scavengers play a role in this, but are not the
only organisms involved. There are specific cycles for carbon/oxygen, water, nitrogen, phosphorus,
sulphur, and others.
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Biogeochemical Cycles are the flow of chemical elements and compounds between living organisms
and the physical environment. Chemicals absorbed or ingested by organisms are passed through the
food chain and returned to the soil, air, and water by such mechanisms as respiration, excretion, and
decomposition. As an element moves through this cycle, it often forms compounds with other elements
as a result of metabolic processes in living tissues and of natural reactions in the atmosphere,
hydrosphere, or lithosphere. (Definition from www.dictionary.com.)
The Carbon Cycle
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CarbonCycle.html
Carbon exists in the non-living environment in the form of CO2 in the atmosphere (HCO3 when
dissolved in water), carbonate rocks such as limestone (CaCO3), fossil fuels and decaying organic
matter (e.g. humus in the soil).
Carbon enters the living world by the action of autotrophs, which convert carbon dioxide to
carbohydrates during photosynthesis (plants & algae) and chemosynthesis (bacteria & archaeans… the
only chemoautotrophs).
Carbon returns to the non-living world by cellular respiration, burning, and decay.
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Factors Affecting the Distribution of Species
Plants
 Temperature: most plants live in moderate temperate zones
 high temperatures denature enzymes & retard growth of plants
 low temperatures decrease enzyme activity
 freezing temperatures inactivate enzymes
 Water: vital to all living things!
 needed for enzyme activity, transport, photosynthesis and support
 adaptations to minimize water loss by transpiration
 Light:
 necessary for photosynthesis and flowering
 dark areas have few (if any) plants
 Soil pH: important for absorption of nutrients
 acid can cause desertification; limestone can be used to neutralize
 Salinity: affects absorption through osmosis
 high salinity causes water loss (halophiles live in high salt!)
 Mineral nutrients: many vital functions
 Nitrogen for proteins, enzymes, nucleotides, vitamins, etc.
Animals
 Temperature: high animal distribution in the tropical rainforest
 suitable temperature & high availability of producers
 Water: vital to all living things
 low animal distribution in deserts
 Breeding Sites: for growth and protection of young
 high diversity in areas of varied topography
 Food Supply: animals are heterotrophs
 another reason for high animal diversity in the rainforest
 Territory: for feeding, mating & protecting young
 territoriality may be seasonal
Niche & The Principle of Competitive Exclusion
Niche = the status of an organism within its environment and community (affecting its survival as a
species). No two species can live in the same niche, therefore there is competition for the resources of
the land and only one species will survive.
• Fundamental niche is the potential mode of existence of a species, given its adaptations
• Realized niche is the actual mode of existence, which results from adaptations and competition
with other species
Competitive exclusion is where two species need the same resources and will compete until one
species is removed. Inevitably, one species would be more capable, gathering more resources or
reproducing more rapidly until the other species was run out of existence. Russian ecologist G.F.
Gause demonstrated this concept scientifically using Paramecia:
Species grown
separately
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Species grown
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Community Ecology
Interactions between Species:
• competition – for resources such as food, water, shelter, territory, even mates (within a species)
•
herbivory – a relationship between a plant and an animal species, where the animal is a
herbivore, obtaining energy and organic compounds by consuming part of the plant (rabbits
eat grass, giraffes eat leaves off trees)
•
predation – a relationship between two animal species, where a carnivore (the predator) hunts
and kills another animal; the predator is often larger in size than the prey (lions hunt gazelles,
owls hunt mice)
•
parasitism – a relationship between a host organism and its parasite; the parasite benefits while
the host is harmed (tapeworms are intestinal parasites of many mammals, mistletoe is a
parasitic plant that lives on the branches of a tree or shrub)
•
mutualism – a relationship between two different species where both organisms benefit (lichens
are a mutualistic relationship between a fungus and an alga, pollination benefits both the plant
and its pollinator)
Gross Production, Net Production, and Biomass
•
•
•
Gross production is the amount of material fixed by plants in the process of photosynthesis.
Net production is the amount of material that stays in the body of the plant after spending some
material on respiration.
Biomass is the dry weight of organic matter comprising a group of organisms in a particular
habitat.
Gross Production – Respiration = Net Production
If a plant produces 2.0 kg of organic material in a month, and uses 0.95 kg for respiration, the net
production is (2.0 – 0.95) kg = 1.05 kg.
Population Ecology
The following contribute to the growth of a population:
•
natality (birth rate)
•
mortality (death rate)
•
immigration (individuals moving in)
•
emigration (individuals moving out)
The change in a population can be determined as follows:
growth rate =
(natality + immigration) - (mortality + emigration)
× 100%
original population size
€
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Growth of a population typically follows a sigmoid (S-shaped) curve:
Number of Bacteria
Growth of Bacteria
1
2
3
90
80
70
60
50
40
30
20
10
0
Time (hh:mm)
The sigmoid curve can be divided into three zones:
1. Exponential – no limits on population growth, resulting in a rapid increase in population size.
2. Transitional – intraspecific competition for resources (e.g. food, water, shelter) causes a
decrease in the population growth rate.
3. Plateau – no further increase in the population’s size; the habitat’s carrying capacity has been
reached.
Carrying capacity is the maximum number of a species that can be supported by the environment.
Factors Limiting Population Growth
Density-Dependent Factors affect the population more as the population density (# of individuals per
unit area) increases.
•
Intraspecific competition
•
Predation
•
Disease
Density-Independent Factors affect a part of the population regardless of population density.
•
weather
•
natural disasters
Extrinsic Population-Limiting Factors are those factors that come from outside the population.
•
food supply
•
predators
•
disease
•
weather
Intrinsic Population-Limiting Factors are those factors that come from within the population, including
the organism’s anatomy, physiology and behaviour.
•
intraspecific competition
•
self-destructive behaviour (e.g. lemmings)
•
reproductive behaviours (e.g. only males with blue & purple fur will mate)
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Types of Populations
Open Populations are affected by natality, mortality, immigration & emigration.
•
Canada’s human population
•
A forest
Closed Populations are only affected by natality and mortality.
•
Earth’s human population
•
a test tube
•
a fish tank
Population Sampling
In population studies, it is often useful to know the size of the population in question. Because it is
often difficult to count every individual in a population, ecologists use different methods of estimating
a population’s size.
Random Sample: a method to ensure that every individual in a population has an equal chance of
being observed
In order for a population study to be effective, the sample must be both random and as large as
possible. Population studies are often conducted over a period of days, months or years, depending on
the species being studied.
Quadrat Study
This can be accomplished in different ways.
1.
The habitat area can be marked off in a grid, and random sections of the grid are sampled.
The sample is used to determine an estimated population size.
http://fieldtrip.britishecologicalsociety.org/rocky%20tour%201/rocky%20shore%20tour%20web/a%20quadrat.jpg
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A hoop or ring of known area is placed randomly in the habitat, and individuals counted.
http://itserver.footscray.vic.edu.au/ARCgrasslands/Emily__Hayley_Quadrat.jpg
Line Transect
This may also be done in different ways:
1.
Combined with the quadrat study … the quadrat (hoop) is placed at intervals along a line,
and only those individuals within the quadrat are counted.
2.
All individuals observed along a transect line are counted, and several transects are
combined to estimate population size.
Capture-Mark-Release-Recapture (HL only)
With mobile organisms such as most animals, it is often difficult to use a quadrat or transect study to
estimate population size.
1. Capture a random sample of the organism to be counted.
2. Mark each captured individual with a tag or other marking (shouldn’t interfere with the
organism’s chances of survival).
3. Release tagged individuals back into the habitat.
4. Capture a second random sample, counting how many are marked.
We use the Lincoln Index (below) to estimate the population size:
Population Size =
n1 × n2
n3
n1 = size of 1st sample
n2 = size of 2nd sample
€ in 2nd sample
n3 = # of marked individuals
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Classification
Why do we need to classify organisms?
When we classify organisms, we arrange them into groups. Classifying organisms makes them easier
to study.
•
Classification helps to organize the large number of species into smaller groups, which
helps to make sense of the vast diversity of organisms around us.
•
Classification attempts to reflect evolutionary links. Species that are in the same group
probably share characteristics because they have evolved from a common ancestor, so the
classification of groups can be used to predict how they evolved.
•
Classification uses common characteristics to group organisms so it helps to predict the
characteristics of new members of the group. If several members of a group have a
particular characteristic, it is likely that another species in this group will have the same
characteristic.
How are Organisms Classified?
All organisms are initially divided into general groupings based on common characteristics such as cell
structure and nutrition. The most general division is into domains:
1. Archaea – the archaebacteria, primitive unicellular organisms that live in hostile environments
(e.g. high temperature, low pH, high salt) and whose cells do not have a nucleus
2. Bacteria – the eubacteria, unicellular organisms, also without a nucleus, but living in almost
any environment (e.g. a mammal’s large intestine, in soil)
3. Eukarya – all organisms whose cells contain a nucleus, which includes animals, plants, fungi
and single-celled organisms such as Amoeba and Paramecium
The next grouping of organisms is into kingdoms.
Kingdoms
Common Characteristics
Archae- unicellular
bacteria
- no nucleus (prokaryotic)
- few organelles
- live in hostile environments
Eubacteria
Protista
-
unicellular
prokaryotic
few organelles
live in many environments
unicellular; some simple
multicellular forms
have a nucleus (eukaryotic) and
numerous membrane-bound
organelles
some autotrophs, most are
heterotrophs
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Examples
- methanogens, bacteria which produce
methane gas as a by-product of cellular
metabolism
- extreme halophiles, bacteria that can
survive in environments with as much as
15% salt
-
Streptococcus group A, which causes strep
throat
Escherichia coli, which lives in the colons
of mammals and is found in faeces
Giardia, which causes giardiasis, or
“beaver fever”
Euglena, which have a flagellum and
chloroplasts
Slime moulds, fungi-like protists that can
be unicellular or multicellular
Algae, which may be unicellular or
multicellular
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Kingdoms
Fungi
Plantae
Animalia
Notes for Ecology & Conservation
Common Characteristics
- unicellular, multinucleate or
multicellular
- eukaryotic
- extra-cellular digestion
- cell wall contains chitin
- multicellular
- eukaryotic
- photosynthetic (autotrophs)
- cell wall contains cellulose
- multicellular
- eukaryotic
- heterotrophs
- no cell wall
Examples
- yeasts are unicellular fungi
- mushrooms are multicellular fungi
-
mosses
ferns
conifers
flowering plants
sponges
corals
insects
birds
mammals
Within a kingdom, organisms are further grouped according to common characteristics. The hierarchy
of classification levels, or taxa, is as follows:
Species is the most specific, and is the only true classification. It is a group of organisms with similar
characteristics, which can interbreed and produce fertile offspring.
Genus (pl. genera) is a group of species that are similar.
Family is a group of genera that are similar.
Order is a group of families that are similar.
Class is a group of orders that are similar.
Phylum (pl. phyla) is a group of classes that are similar.
Kingdom is a group of phyla that are similar.
Kingdom
Phylum
Class
Order
Family
Genus**
Species**
House Cat
Animalia
Chordata
Mammalia
Carnivora
Felidae
Felis
domesticus
Redwood Tree
Plantae
Coniferophyta
Pinopsida
Pinales
Taxodiaceae
Sequoia
sempervirens
Button Mushroom
Fungi
Basidiomycota
Hymenomycetes
Agaricales
Agaricaceae
Agaricus
bisporus
** The genus and species name are used as the organism’s scientific name. These names are standard
within the scientific community, and are generally based in Latin. Latin names are italicised, with the
Genus name capitalized, and the species name not capitalized. Because this gives each organism a
two-word name, we call it binomial nomenclature – Carolus Linnaeus, a Swedish botanist & physician
originally devised this system in the 1700s.
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Representative Plants:
Phylum (Division)
Bryophyta
e.g. mosses
Filicinophyta
e.g. ferns
Coniferophyta
e.g. conifers
Angiospermophyta flowering plants
Notes for Ecology & Conservation
Roots, Stems & Leaves
Rhizoids instead of true
roots. Simple stems &
leaves.
Have true roots, leaves,
and non-woody stems.
Shrubs or trees with roots,
narrow leaves & woody
stems.
Roots, leaves & stems with
variable structure.
Representative Animal Phyla:
Porifera
- no clear symmetry (asymmetrical)
- attached to a
surface
- pores through
body
- no mouth or
anus
- e.g. sponges
Max.
Height
0.5 m
Reproductive Structures
15 m
Spores produced in sporangia,
usually on the underside of leaves.
Seeds are produced in cones. No
flowers!
100 m
100 m
Spores produced in capsules, which
develop at the end of a stalk.
Seeds are produced in flowers.
Fruits disperse seeds.
Cnidaria
- radial symmetry
- tentacles
- stinging cells (nematocysts)
- mouth but no
anus
- e.g. jellyfish,
corals, sea
anemones
Platyhelminthes
- bilateral symmetry
- flat bodies
- unsegmented
- mouth but no
anus
- e.g. Planaria,
tapeworms
Annelida
- bilateral
symmetry
- bristles often
present
- segmented
- mouth and
anus present
- e.g.
earthworms,
leeches
Mollusca
- muscular foot
and mantle
- shell usually
present
- segmentation not
visible
- mouth and anus present
- e.g. slugs, snails, clams, squids
Arthropoda
- bilateral
symmetry
- exoskeleton
- segmented
- jointed appendages
- e.g. insects, spiders, crabs
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Dichotomous Keys
A dichotomous key is a biological tool for identifying unknown organisms to some taxonomic level
(e.g. species, genus, family, etc.). It is constructed of a series of couplets, each consisting of two
statements describing characteristics of a particular organism or group of organisms. A choice between
the two statements is made that best first the organism in question. The statements typically begin with
broad characteristics and become narrower as more choices are required.
A dichotomous key is constructed of a series of couplets, each consisting of two separate statements.
For example:
Couplet
1a.
1b.
Seeds round…………………………..soybeans
Seeds oblong………………………….2
(The second statement indicates that you need to go to couplet “2”)
Couplet
2a.
2b.
Seeds white……………………………northern beans
Seeds black……………………………black beans
By reading the two statements of each couplet, you progress through the key from typically broad
characteristics to narrower characteristics until only a single choice remains. As long as the correct
statement of each couplet is chosen, and the unknown organism is included in the key, a confident
identification is usually achieved.
Biodiversity
What is biodiversity?
It is the variety of life on our planet. Diversity can be observed between:
•
individuals
•
sub-species (anatomically distinct, but able to interbreed successfully)
•
species
•
biological communities
•
ecosystems
About 10 000 new species are discovered each year. Most of these are insects and other invertebrates;
however there are 1-5 new birds and 1-5 new mammals discovered each year, mostly in the tropics.
Examples of newly discovered species include:
•
Peruvian beaked whale, about the size of a dolphin, discovered in 1976
•
Cryptic warbler, a new species of songbird, discovered in Madagascar in 1992
New ecosystems are also being discovered:
•
Hydrothermal marine vents on the ocean floor are like submarine hot springs, and are
home to hundreds of species, including crabs, shrimps, clams and fishes.
•
Anchialine caves, which are flooded caves that are under land, near the coast, and have no
direct surface connection with the sea. They are home to many unique crustaceans and
other arthropods.
•
Lava tubes, which are caves beneath lava flows in Hawaii, and are inhabited by many
species of animals that are adapted to life in complete darkness. The primary food source
for these animals is the roots of ohia trees that hang down into the caves.
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It is estimated that there are 5 million species of organisms on Earth; 2.1 million of these are insects!
The diversity of species in an ecosystem may be quantified using the Simpson diversity index, which
takes into account the number of species present and the relative abundance of the species. The
inverse or reciprocal of the number calculated represents the probability that two randomly selected
individuals from the ecosystem are of the same species.
The formula is:
D=
N ( N −1)
∑ n( n−1)
N is the total number of individuals in the area
n is the €
number of individuals per species
D is the diversity index
Example:
Two islands each have populations of four species:
Island 1
Species
A
B
C
D
Totals
n
345
260
342
598
1545
n(n-1)
118 680
67 340
116 622
357 006
659 648
1/D = 0.276, or 27.6% chance that two randomly selected individuals are the same species.
Island 2
Species
n
n(n-1)
A
50
2450
B
20
380
C
40
1560
D
1250
1 561 250
Totals
1360
1 565 640
1/D = 0.847, or 84.7% chance that two randomly selected individuals are the same species.
The diversity index values indicate that Island 1 has greater biodiversity than Island 2.
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A high value for D suggests a stable and ancient site. A low D value could suggest pollution, recent
colonization or agricultural management (e.g. a monoculture). The index of diversity is usually used in
studies of vegetation, but can also be applied to animals or diversity of all species.
o
One of the consequences of the pollution caused by the Gulf war was that the diversity of
marine species around Bahrain dropped dramatically.
Biomes
• Biome = a major life-zone over an area of the Earth, characterised by the dominant plant life
present
• Biosphere = the inhabited part of Earth; includes lower atmosphere, land, and water
Biome
Desert
Grassland
(Temperate)
Savannah
(Tropical
Grassland)
Temperate
deciduous
forest
Boreal
coniferous
forest
Tundra
Tropical
Rainforest
Major Biomes of Earth
Climate
Plant Life
Hot and dry; limited or unpredictable
Ephemerals are dormant until there is
rainfall.
rainfall, and then go through a quick life
cycle to produce seeds.
Succulents such as cacti survive year-round
due to water-saving adaptations and
protective measures such as spines.
Moderately dry, with hot summers and
Perennial grasses, with some broad-leaf
cold winters.
flowering plants that bloom when the grasses
are less predominant – at the start/end of
growing season.
Three seasons: cool and dry, hot and
Grasses with interspersed, individual trees.
dry, hot and wet.
Tree population limited by elephants,
lightning
Four seasons: mean annual temperature Broad-leaf deciduous trees (maple, oak,
10ºC; 75-150 cm rainfall
birch, beech), mosses, ferns, and shrubs.
Temperature varies from -50ºC to 30ºC;
eight or more months with temperatures
below 10ºC. Annual rainfall between 20
& 75 cm.
Low temperatures, resulting in
permafrost.
Arctic Tundra occurs in the far north and
Antarctica, while Alpine Tundra occurs
well above the tree line on the highest
mountains.
Areas of heavy rainfall; near the equator.
Coniferous (needle-leaved) trees such as pine
and fir; mosses, lichens
Limited growing season in summer and poor
soil conditions limit plant life. No trees.
Dominant plants are trees (30-50 m);
epiphytes grow on the branches. Most
diverse biome on Earth.
The distribution of biomes within the biosphere is affected by both rainfall and temperature.
• Temperature influences organisms’ metabolism; many plants have temperature-dependent
phases of their life cycles, such as seed germination after a period of colder temperatures.
• Rainfall is critical, because of the necessity of water for supporting life. Plants that are adapted
to a hot, wet climate (e.g. tropical rainforest) would not survive a hot, dry climate (e.g. desert).
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Image from: http://www.bcscience.com/bc10/images/0_quiz_01.1_09.gif
Ecological Succession
When land is exposed, it doesn’t remain so forever. Organisms quickly move in to the area in a
predictable pattern, changing the area over time until it reaches a stable community. This process of
change is known as ecological succession. The process of succession is also referred to as a sere, with
the stages called seral stages.
•
•
Primary succession occurs when new land is formed, at river deltas, sand dunes, and even lava
flows. There is little to no established soil for plants to grow in.
Secondary succession occurs in areas where the vegetation has been disturbed, by fire or clearcutting, for example.
Primary succession most often begins with bare rock, the erosion of which forms the mineral portion of
soil. Humus, the organic portion of soil, forms from decaying plant and animal matter, and faeces.
Until the soil is fully formed, it retains little water (this is also true for sand) even if it is plentiful. A sere
that begins in dry conditions such as this is called a xerosere (xerophytes are plants adapted to dry
conditions). Primary succession may also occur in aquatic conditions such as a spring-fed pond; this is
a hydrosere.
•
•
•
Pioneer plants are the first plants to live in the new area. Usually, they are small and adapted
to life with limited water. Lichens (a symbiosis between a fungus and an alga) are typical
pioneer plants.
Mosses are able to grow once some soil has formed, including humus contributed by the
lichens. Other small, herbaceous (i.e. having non-woody stems) plants follow the mosses.
Their roots prevent soil erosion, and their deaths enrich the soil by adding more humus.
The pattern continues with a series of ever-larger plants overtaking the previous community,
determined largely by the biome in which the succession is occurring.
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The final stage is the climax community, a stable ecosystem with characteristic plant and
animal life for the biome.
Not every climax community is a forest – introduction of herbivores could change the pattern of
succession to result in grassland instead. No matter where succession occurs, each successive stage
has greater biodiversity than the one it replaced.
Secondary successions occur much more quickly because there is soil present. While primary
succession could take several hundred years, secondary succession is often complete within 100 years.
http://www.geogonline.org.uk/images/lithosere.gif
A hydrosere
http://www.geogonline.org.uk/images/hydrosere.gif
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Conservation in the Rainforest
Conservation is important on a global scale. While many of these arguments work for any ecosystem,
the rainforest in particular is a good example to use, since biodiversity is typically very high in
rainforests.
Ethical arguments
“We did not inherit the earth from our parents; we are merely borrowing it from our children.”
(Kenyan Proverb)
•
•
•
Every species has a right to life, regardless of whether it is useful to humans or not.
The wildlife of each area has cultural importance to the local human population and it is
therefore wrong to destroy it.
It would be wrong to deprive humans in the future of the rich experiences that the Earth’s
biodiversity provides us.
Ecological arguments
• Cutting down the rainforest will remove nutrients from the area
• The remaining soil is not capable of sustaining many crops.
• Erosion will cause further destruction.
• Loss of the plant life in the rainforest can increase the amount of CO2 in the atmosphere,
increasing the greenhouse effect and global warming.
• Ecologists predict that if we continue without change, nearly half of the world’s species will
disappear in the next 500 years.
Economic arguments
• Many of our medicines originate from plants. The rosy periwinkle, once on the verge of
extinction, is now used to produce medicine used in chemotherapy.
• The mahogany tree, used for furniture, is a rainforest species.
• Recreation and tourism will be affected.
Aesthetic arguments
• Natural ecosystems and species in the wild are beautiful and give us great enjoyment.
• Painters, writers and composers have been inspired by the nature around them.
• “Extinction is forever.”
Extinction is Forever! (HL only)
First, some definitions:
• extinct - species no longer exist anywhere.
• extirpated - species no longer exist in the wild in Canada (or another region in which it had
been previously found), but they occur elsewhere.
• endangered - species face imminent extinction or extirpation.
• threatened - species are likely to become endangered if limiting factors are not reversed.
• vulnerable - species are of special concern because of characteristics that make them
particularly sensitive to human activities or natural events.
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Extinct Animals:
Although prehistoric animals such as dinosaurs and the sabre-tooth tiger are extinct, they are
considered to be natural extinctions. Historic extinctions, on the other hand, are most often caused by
the actions of humans.
•
The Great Auk – the first North American bird species to become extinct in historic times, it
was the only flightless bird in North America, and resembled the penguins now found only in
the southern hemisphere. Great auks and their eggs were a source of food to the native people
of Newfoundland, but it was the Europeans who caused its extinction, by over-hunting them for
food and feathers. The last known nesting pair was killed in 1844 by men who were more
interested in the money the birds would bring them.
•
The Sea Mink – twice the size of the American Mink, it was hunted to extinction for its fur. The
last known member of the species was captured in New Brunswick in 1894.
Extinct Plants:
We often think of animals when asked about extinct species, but plant species have become extinct in
historic times, also.
•
•
Macoun's Shining Moss is the only Canadian endemic plant to have gone extinct since the
1500’s. It was found only in a small part of Ontario, and clear-cutting of the region where it
was found (i.e. habitat destruction) caused its extinction.
Kerala Legume Tree, was found only in India. It is now extinct due to habitat loss and has not
been seen since 1870.
Conservation of Endangered Species: in situ vs. ex situ methods (HL only)
Terrestrial and aquatic nature reserves are places where the endangered animal is found in its own
natural habitat and is not allowed to be overtaken by humans. This keeps the animals out of danger
zones and allows them to live and reproduce naturally in their own environment. Most animals
typically tend to survive at a much greater rate using in situ conservation, and preserving their habitat
allows other species to live there also, thus preserving other animals and biodiversity.
Sometimes in situ conservation methods are not feasible, and other methods (ex situ) are necessary. In
captive breeding, animals kept in zoos or parks are allowed to reproduce in order to give them a
chance to increase in number, with the possibility of eventually releasing some of the offspring into the
wild. Botanic gardens are where most of the known plant species are planted in controlled
environments to maintain their species. Seed banks are where seeds are kept, since they stay in good
condition for thousands of years.
Conservation of Species (HL only)
The International Union for the Conservation of Nature (IUCN)
involves 200 governments and 300 private organizations. It
focuses on conservation of species and habitats. The IUCN
publishes Red Data Books, which are lists of endangered
species. The Convention on Trade in Endangered Species
(CITES) is an offshoot of the IUCN, and regulates trade in
organisms or their products. For example, CITES banned trade
in ivory, which was successful in reducing poaching of
elephants.
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The IUCN has classified and analyzed areas that have various degrees of biodiversity protection. There
are eight categories of protected areas. The first five deal with maintaining biological diversity:
•
scientific reserves
•
national parks
•
natural monuments
•
nature reserves
•
wildlife sanctuaries
The other three categories focus on controlled resource exploitation (e.g. national forests).
One method of conservation is to set up nature reserves. The management of nature reserves involves:
•
Control of Alien Species: Alien species must be eliminated, particularly predators and
invasive plants.
•
Restoration of Degraded Areas: Areas degraded by human activities (e.g. logging,
recreation) must be restored.
•
Recovery of Threatened Species: Special measures may be needed to help encourage
threatened species. For example, supplementary feeding or clearing of vegetation may be
required.
•
Control of Exploitation by Humans: Exploitation by humans must be controlled. For
example, hunting and fishing would be limited or restricted.
In 1992 by the UN Conference on Environment and Development organized the Rio Convention (also
called the Earth Summit) in Rio de Janeiro. One of the results of the Rio Convention was the
Biodiversity Treaty – countries signing the treaty agreed that richer countries would give money to
poorer countries for the conservation of biodiversity.
The World Wildlife Fund (WWF) aims at the conservation of biodiversity by encouraging sustainable
use of resources. The WWF is not linked to any government. Greenpeace is another nongovernmental organization that is concerned with biodiversity; however, its methods tend to be a bit
more controversial than those of the WWF.
r-Strategists and K-Strategists (HL only)
Ecologists classify species based on their reproductive strategies.
r-Strategists are often pioneer species, colonizing new habitats rapidly. Characteristics of r-strategists
include:
• reproduce themselves rapidly
• high mortality
• produce large numbers of offspring
• short life spans
r-Strategists often occur in numbers well below the carrying capacity for the habitat. Many weeds (e.g.
ragweed), insects, and rodents are r-strategists.
K-strategists move into settled, stable habitats. Characteristics of K-strategists include:
• reproduce themselves slowly
• low mortality
• produce less offspring
• long life spans
Once established, K-strategists compete successfully for resources, and population levels remain
relatively constant – at the carrying capacity for the habitat.
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Indicator Species and Biotic Indices as a Measure of Environmental Change (HL only)
Indicator species are unique environmental indicators as they offer a signal of the biological condition
of a watershed or ecosystem. They are also a warning that pollution has entered the food web. The
term is actually a bit misleading – indicator species generally refer to whole groups of organisms of a
particular type, flora or fauna.
In general, indicator species live all or most of their lives in water, and differ in tolerance to amount
and type of pollution. There are four major groups of indicator species:
1.
Fish are excellent indicators of the health of a watershed or aquatic ecosystem.
a. They are easy to collect with the right equipment.
b. They live for several years.
c. They are easy to identify in the field.
2.
Aquatic Invertebrates live in the bottom parts of our waters (benthic organisms). They are
also good indicators of watershed health.
a. They stay in areas suitable for their survival.
b. They are easy to collect.
c. They are easy to identify in a laboratory.
d. They often live for more than one year.
e. They have limited mobility.
f.
3.
They are integrators of environmental condition.
Periphyton is benthic algae that grow attached to rocks or other plants. They are good
biological indicators due to:
a. a naturally high number of species
b. a rapid response time to both exposure and recovery
c. ease of sampling
d. tolerance or sensitivity to specific changes in environmental condition are known for
many species
4.
Macrophytes are aquatic plants, growing in or near water, submergent (under water),
emergent (growing out of water), or floating. Lack of macrophytes in an ecosystem can
indicate water quality problems such as herbicide use or salinisation.
A biotic index (BI) is a rating of water quality based on organisms living in a stream. They cannot be
determined for lakes or ponds. BI scores are related to dissolved oxygen levels in streams that are
affected by inputs to streams. The BI represents stream health over time. Biotic indices are usually
regionally developed.
Marine Ecosystems and Fishing (HL only)
The fishing industry vastly increased in scale during the 1970s and 1980s. The number of large ships
fishing the world’s oceans doubled and the efficiency of the process was also greatly improved. Nets
were catching smaller fish, which were able to escape previous nets in use. Factory ships, sonar fish
finders and even helicopters have been used to increase the annual catch.
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Some examples:
•
The Grand Banks, off the coast of Newfoundland, has long been a cod fishing-ground. In
the early 1990s, the Minister of Fisheries announced that the Grand Banks cod population
had reached commercial extinction, and ordered a moratorium on the cod fishery; this put
25 000 people out of work.
•
The North Atlantic blue fin tuna is one of the fastest and largest fish in the sea. Until the
1960s it was used only for cat food or sport fishing, but then started being sold in Japan for
use in sushi, and its numbers have declined ever since. Tuna fishing is regulated, but due
to its commercial value it will likely be hunted to extinction.
•
Shark fishing was done mainly for sport until the mid-1970s, when it was marketed as a
cheap alternative to swordfish (also greatly over-fished). The industry peaked in the mid1980s and has plummeted since then.
•
Sturgeon fish are hunted for their eggs, which are used in caviar. Four of the eight North
American species are listed as endangered or threatened.
Invertebrate fisheries are also an issue. Crab, lobster shrimp and other species are at risk from overfishing.
•
•
40% of the world’s shrimp is supplied by aquaculture in countries such as Thailand,
Bangladesh, and the Philippines. These countries are being pressured to convert natural
mangrove forests and other ecosystems into shrimp farms, seen as an inexpensive way to
increase earnings from the industrialized world. However, this would occur at a great
environmental cost, as it would destroy habitats for other fish and shorebirds, and could
cause erosion and flooding. Half the world’s mangrove forests have disappeared, with
more than 50% of these lost to shrimp farms.
Nearly 70 species of mussels are currently endangered, largely because the United States
exports $50 million worth of mussel shells to Japan every year for use in the cultured pearl
industry.
Regulation of Fishing
In order to conserve fish populations, the number of fish caught is restricted. In November 1998, the
United Nations Food and Agriculture Organization adopted a series of measures to monitor and
manage the world’s fishing fleets:
•
regularly assessing harvesting capacity of fleets
•
maintaining national records of fishing fleets
•
developing and implementing national capacity management plans
•
reducing and progressively eliminating subsidies that contribute to the build-up of fishing
capacity
In addition, the FAO will develop a global register of all fishing fleets operating on the high seas and
begin to collect information needed for further analysis of the causes of overcapacity.
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How can you help?
Eat the following sparingly, if at all:
•
•
•
•
•
•
•
shark (especially shark-fin soup)
swordfish
blue fin tuna
beluga sturgeon
caviar
orange roughy
grouper
Okay to eat:
•
•
•
•
canned tuna
Pacific cod
Atlantic striped bass, mackerel and
herring
Farm-raised trout, catfish, shrimp and
salmon
Human Impact on Ecosystems
The Greenhouse Effect & Global Warming
The greenhouse effect is the rise in temperature caused by the presence of certain gases in the
atmosphere. These so-called greenhouse gases include water vapour, carbon dioxide, methane and
nitrous oxide, and act the same way the glass walls of a greenhouse do.
A greenhouse is an effective place to grow plants all year long because its glass walls allow in plenty of
light, and also trap the heat that is released when light is absorbed by objects inside. This means that
even in the coldest winter months, the greenhouse is toasty warm.
Image from http://generalhorticulture.tamu.edu/lectsupl/Temp/P34f1.gif
Without the presence of some greenhouse gases in the atmosphere to trap energy, the Earth’s average
temperature would be about 60°F colder. Some greenhouse gases are emitted into the atmosphere by
natural sources. For example, swamps and marshes emit methane, while most organisms give off CO2
during cellular respiration. However, increases in the emission of greenhouse gases into the
atmosphere over the last several decades have been primarily a result of human activity, and has
resulted in global warming. Over the past century, the Earth’s average temperature has increased by
1°F.
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While 1°F does not seem like a large increase, it is still enough to affect global climates – particularly
rainfall patterns. Plus, scientists studying the greenhouse effect have predicted that global temperatures
will increase by between 2°F and 6°F over the next century. This may also lead to a rise in sea level,
and other impacts on plants, wildlife and humans.
How do humans contribute to the greenhouse effect?
•
Burning fossil fuels (
•
Deforestation (
•
•
Dairy/beef farming (
Landfills (
)
)
)
)
How might global warming affect us?
•
•
•
Changing climates will affect habitats and ecosystems worldwide – in the past, these
changes have been gradual, allowing organisms time to adapt – this may not be the case in
our future.
Warmer temperatures will contribute to the melting of glaciers – this increase in liquid
water will cause a rise in sea level, which will affect coastal habitats and urban areas.
Warmer temperatures in regions that are currently colder may mean that new crops can be
grown – but it may also bring droughts to other places where we currently grow crops.
What can we do to reduce the greenhouse effect & global warming?
•
•
•
•
•
Conserve electricity – power plants are huge emitters of greenhouse gases.
Bike, walk, carpool or take public transit to reduce emissions by personal vehicles.
Plant trees – trees love CO2!!
Recycle, and buy environmentally friendly products that won’t end up in a landfill
somewhere.
Investigate the power of the sun – there are lots of products available that use solar energy –
you can even charge a cell phone using solar energy!
The Ozone Layer & UV Radiation
Ozone (O3) is a fairly rare molecule in our atmosphere – about three molecules of ozone for every ten
million molecules of air. 90% of this ozone is found in the stratosphere – a layer of Earth’s atmosphere
that ranges from about 10 km to 50 km above Earth’s surface. The remaining 10% is found in the
lower atmosphere, the troposphere.
Stratospheric ozone absorbs biologically harmful UV-B rays, so that only a small amount reaches
Earth’s surface. This absorption creates heat, making the stratosphere increase in temperature as
altitude increases. In the lower atmosphere, however, ozone is considered to be a pollutant, and has
been demonstrated to have harmful effects on crop production, forest growth, and human health.
UV radiation makes up about 8% of the total solar radiation that reaches Earth’s surface. Biological
molecules may absorb UV radiation, and bonds between atoms may be broken – because of this, UV
radiation is harmful to organisms and can do permanent damage. It should not
be confused with absorption of solar radiation in the visible spectrum (necessary for photosynthesis) or
infrared (heat).
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UV radiation can kill phytoplankton, the sea-going organisms that account for a significant portion of
net photosynthesis that occurs in the biosphere. The radiation can also retard growth of terrestrial
plants by slowing their rate of photosynthesis, usually a result of irradiative damage and subsequent
mutations caused in plant leaves. High levels of UV light can also kill the symbiotic bacteria that fix
nitrogen in the root nodules of legumes. UV rays cause skin cancer in humans in prolonged exposure
or in very high dosages, and can also weaken and potentially destroy the cells of the immune system.
Depletion of the Ozone Layer
Chlorine reacts with ozone, converting it to oxygen, in an irreversible reaction. One chlorine atom
can react with 100 000 ozone atoms. The main source of chlorine atoms in the atmosphere is CFCs,
chlorofluorocarbons, used for over 50 years as a refrigerant and as propellants in aerosol cans.
O + Cl → ClO + O
3
2
ClO + O → Cl + O
2
Since atomic oxygen is present in the atmosphere from the ozone-production cycle, the chlorine atoms
are regenerated by the second reaction and can go on to degrade more ozone.
€
Image from http://www.ozonedepletion.info/education/part3/Image5.gif
To reduce
the release of
ozonedepleting
substances into the atmosphere, filters can be fitted on factory chimneys to absorb and react with gases
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before they escape into the atmosphere, removal of sulphur from gases before they are emitted into the
atmosphere, using alternative sources of energy such as wind, hydroelectric, solar, tidal, geothermal
and others, use of methane and alcohol as fuels since they do not release sulphur and other harmful
gases into the atmosphere. Two of the largest sources of ozone-depleting substances come from the
production of recycling refrigerants and the use of chlorofluorocarbons (CFCs) for propellants in spray
cans, hairspray, etc. In order to reduce these sources, a ban on CFC-based propellants has been
enacted, and most corporations now recycle the refrigerants used rather than produce entirely new
ones.
Bioaccumulation & Biomagnification
Bioaccumulation refers to an increase in the concentration of a chemical in the tissue of an organism
over time. Whereas, biomagnification refers to the increased concentration of a toxic chemical the
higher an animal is on the food chain.
Chemical toxins build up into higher concentrations as they are passed up the food chain. Toxins that
commonly bioaccumulate include mercury, DDT and other pesticides, and poly-chlorinated biphenyls
(PCBs).
Image from http://web.bryant.edu/~dlm1/sc372/readings/toxicology/biomagnification.jpg
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The Effect of Sewage & Fertilizers on Rivers
Water polluted by raw sewage and nitrate fertilizers will become rich in nutrients in a process called
eutrophication. The algae absorb large amounts of nitrates, resulting in quick growth and reproduction
of these algae. The ecosystem becomes overpopulated with algae (this is called algal bloom).
This blocks the sun from reaching the plants at greater depths and blocks the entry of carbon dioxide
and oxygen from the atmosphere. The algae hit their carrying capacity and start to die quickly,
encouraging the growth of bacteria of decomposition, which increase the biochemical oxygen
demand. They consume a large amount of oxygen, which results in deoxygenation of the water and
aerobic organisms start to die.
Finally, disease-causing anaerobic bacteria and some parasites come in. This makes it a bad spot for
anything to survive in. Raw sewages can also release pathogens into the bathing and drinking water
supplies, causing the risk of human and animal infection when this water is used.
Acid Precipitation
Acid precipitation occurs primarily because of the presence of sulphur oxides and nitrogen oxides in
the atmosphere. These compounds, which come from smokestacks, industries, and vehicle exhaust,
react with water in the air to form acids. These acids can return to the surface as acid precipitation
(rain, snow, etc.).
On the ground, acid precipitation can affect the solubility of minerals in the soil. It can lower the pH of
lakes and contaminate freshwater habitats. It affects fish, amphibians and aquatic invertebrates the
most, due to the destruction of their freshwater lake and river environment.
Use of Biomass for Fuels
Biomass can be used as a source of fuels such as methane and ethanol.
Organic rubbish such as remains of food, are placed in a sealed container. Methanogenic bacteria
such as Methanobacillus and Methanococcus are added. The container must be sealed to ensure
anaerobic reactions. Bacteria decompose organic material in the rubbish to methanoate, ethanoate or
methanol. Bacteria use these things as a source of hydrogen (electrons). The hydrogen is used to
reduce carbon dioxide into methane. The methane is then released. This can be a source of fuel in
factories and industries.
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