ECOLOGY UNIT TEST REVIEW 2025  • All information from Powerpoints and key homework questions.  

Ecosystems. Know information with solid examples.  

Environment, ecology, ecosystems, types of habitats, biosphere- spheres of the earth

The Environment

• All the living and nonliving things that exist on Earth as well as their interactions with each other

• Ideally healthy and sustainable

Ecology

• The study of how organisms interact with each other as well as the environment

• Person = ecologist

Ecosystems

• Complex, self-regulating system formed by the interactions of biotic factors with abiotic factors in a particular area (healthy and sustainable)

• Living (Biotic factors)

  • Living things, their remains, and features associated with their activities (nests)

  • Insects, bears, bacteria, fish, bones, wood

  • Bones and wood are things that come from living things, so they are biotic

• Nonliving (Abiotic factors)

  • Non-living physical and chemical components of an ecosystem (what would be there if there were no living things)

  • Temperature, wind, light, water, rocks, minerals, air

• But… Some things cannot be easily classified as living or nonliving…

• Eg. coral reefs are made by animals but break down over time

What are habitats?

• The place where an organism lives

  • Eg. A bird’s nest in a tree

Two types of habitats:

• Terrestrial (land habitats)

  • Deserts (cacti and rattlesnakes)

  • Tropical rainforests (trees and insects)

  • Frozen Arctic (polar bears, penguins, ice, etc.)

• Aquatic (water habitats)

  • Coral reefs (diverse, colourful fish)

  • Ocean depths (sharks, shrimps)

  • Lakes and ponds (home to fish and stuff)

Biosphere

• A part of the planet (water, land, air) where life exists

Atmosphere

• The layer of gases surrounding Earth 

  • Atmos = vapour (Greek)

  • ~78% nitrogen gas, ~21% oxygen gas

  • Problem is that more carbon dioxide is getting into the atmosphere, blocking sun

  • Role of the atmosphere

    • Acts like a blanket and moderates surface temperature

    • Blocks some incoming solar radiation

    • If we didn’t have an atmosphere, it would be too cold and there would be too much cancer, as there would be nothing blocking the sun rays

Lithosphere

• Lithos = stone (Greek)

  • Earth’s solid outer layer

    • Crust and uppermost mantle (rocky outer shell)

    • Makes up mountains, ocean floors, and the rest of solid landscapes

  • May be 50-150 km in thickness

Hydrosphere

• Hydro = water (Greek)

• All of the earth’s water on, above, or below the Earth’s surface

  • Exists in solid, liquid, and gas form (eg. oceans, lakes, groundwater, clouds)

• 97% OF EARTH’S WATER IS CONTAINED IN OCEANS!

Damage to the lithosphere- human and natural

• Damage to the Lithosphere

  • Man-induced

    • Excavation and drilling (eg. Mining pits, drilling for oil)

  • Natural disasters

    • Earthquakes

Biosphere- what do living things require

• Biosphere

  • Bio = life

  • The zone around Earth where life can exist

    • Some life can exist in one or more spheres

  • Atmosphere: birds

  • Lithosphere: worms, snakes, trees, humans.

  • Hydrosphere: dolphins, whales, catfish, algae

  • The biosphere (atmosphere, lithosphere, and hydrosphere) is important because all living things require the following to survive:

    • Nutrients 

      • Cellular respiration (need energy & nutrients to breathe):

      • C₆H₁₂O₂ + O₂ → CO₂ + H₂O + ENERGY

      • Sugar + Oxygen → Carbon Dioxide + Water + ENERGY

    • Water

Gaia hypothesis, stewardship, sustainability

• Earth behaves like a living organism through interactions amongst the four spheres

• Earth is capable of responding to changes in its environment

  • Can change with incoming sunlight, and maintaining relatively constant internal conditions over long periods of time (like a living cell does)

• The hypothesis is not a scientific concept, but many people feel that if we think of Earth as a living thing, it may encourage and promote a more caring attitude toward our planet and the life that it supports

Ecosystems- biotic vs abiotic, characteristics of living things

• Living (Biotic factors)

  • Living things, their remains, and features associated with their activities (nests)

  • Insects, bears, bacteria, fish, bones, wood

  • Bones and wood are things that come from living things, so they are biotic

• Nonliving (Abiotic factors)

  • Non-living physical and chemical components of an ecosystem (what would be there if there were no living things)

  • Temperature, wind, light, water, rocks, minerals, air 

• But… Some things cannot be easily classified as living or nonliving…

  • Eg. coral reefs are made by animals but break down over time

• Living things typically do these:

  • Move/ respond to stimuli (plants move towards sun...)

  • Reproduce (produce offspring)

  • Take in nutrients (need food)

  • Respire: make energy (cellular respiration : glucose + oxygen → carbon dioxide + water + ENERGY)

  • Excreting wastes ( carbon dioxide, water, urine, feces...)

  • Life cycle: grow and die 🥀

Biotic components of an ecosystem

• Biotic components of an ecosystem

  • Organism: a single individual within a species

  • Population: all the individuals of a species that live in the same area

  • Community: populations of different species living in the same area

• If a place has all these biotic + abiotic components (eg. water, rocks, wind), it is an ECOSYSTEM

Communities- species, habitat, niche

• Communities

  • Species: a group of similar organisms in an ecosystem (eg. grey squirrel and red squirrels)

    • Generally considered the same species if they are sexually compatible (can make a kid together, and that kid is sterile)

  • Habitat: physical environment of an organism

  • Niche: all the interactions of a given species with its ecosystems form the species’ niche

• Whatever the size, each ecosystem is characterized by a distinctive set of characteristics, for example:

  • types of organisms

  • temperature range (including seasons...)

  • rainfall or water depth

Biomes

• Large geographical region that contains similar ecosystems

  • Defined by: type of plants, animals, weather (temperature, amount of rainfall)

• Biomes divided: land vs water

• Biomes combine to make BIOSPHERE: all land, water, air…

• Terrestrial Biomes

  • Deciduous forest: lose leaves in autumn (maples and oaks)

    • Southern Ontario

  • Boreal Forests (Taiga): trees have cones/needles (spruce and fir)

    • Northern Ontario

  • Tundra: no trees, small shrubs, hardy grass, moss

    • Northern Ontario coastline

  • Grasslands: few trees (shrubs and grasses)- 

    • Manitoba, Saskatchewan, some Alberta

  • Temperate coniferous forests: many diff. types of needle and cone bearing trees (Douglas fir, Sitka spruce, etc.)

    • Western B.C

• Aquatic Biomes

  • Water based: marine and freshwater

    • Marine: high salt content

      • Oceans: coral reefs, ocean floor, open ocean

    • Freshwater: low salt content

      • Lakes, streams, rivers, wetlands

Sustainability 

• The ability to maintain natural ecological conditions without interruption, weakening, or loss of value (ecological balance)

  • Living organisms continue to interact and to reproduce indefinitely (forever!)

  • Taking/using less to prevent environmental collapse

• Most ecosystems are sustainable; they maintain a relatively constant set of characteristics through natural processes over a long period of time

Human activities affecting sustainability

• Human activities often disrupt ecosystems by changing their biotic and abiotic features, rendering them unsustainable.

  • Over-hunting/fishing 

    • Clear-cutting & logging 

    • Construction 

    • Mining

Artificial ecosystems

• Created by humans

• Must be maintained by human actions (not sustainable on its own)

  • Urban park

  • Farm

  • Butterfly rainforest 

  • Aquarium

Ecosystems influencing our daily lives

• Ecosystems (natural & artificial) influence many aspects of our daily lives

  • Biotic factors

    • Forestry (trees are valuable to us)

    • Agriculture (farming for food)

    • Tourism (zoos, marine parks, botanical gardens, …)

  • Abiotic factors

    • Sunlight (people in northern environments are more likely to suffer from SAD - seasonal affective disorder - due to low light levels)

    • Air (people living in large urban areas are more likely to suffer from breathing problems; smog)

    • Lakes (provides opportunities for recreational activities)

Nutrient Cycles 

Biogeochemical Cycle: The movement of chemical elements through different media, such as the atmosphere, rocks, soil, bodies of water, and organisms

Nitrogen Cycle:

• 79% of the Earth’s atmosphere is made up of nitrogen gas

All living things depend on the nitrogen cycle. It is required for:

• Cells to create protein

• Synthesis of DNA

• Plant growth(found in fertilizer)

But nitrogen cannot be used in a gas form(must be turned into either Nitrate(NO₃) or ammonia(NH₃) through nitrogen fixation

There are 2 ways to create nitrates

1. Lightning strikes: energy causes nitrogen gas to react with oxygen and make nitrates

2. Bacteria: Majority of nitrates found in the atmosphere are provided by nitrogen-fixing bacteria.This is called Nitrification

That bacteria is found in the soil. The nitrates are good for plants and is used in fertilizer

Denitrification: The process of turning nitrates back into nitrogen gas and returning it to the environment. This is done by decomposing bacteria and animal waste

Too much nitrogen = bad

Excess nitrogen not used by plants wash into water

Eutrophication: Nitrogen and other stuff builds up in lakes

Algal Bloom: Nutrient build up causes algae and weeds to grow on top of water quickly

The oxygen used kills the fish, cuz the plants use the oxygen and the fish don’t have any

The bloom at the top of the lake blocks the sun from reaching bottom plants, they die too

Carbon Cycle

• Carbon is the building block of all things

• Producers must have carbon to photosynthesize

• Consumers eat plants(or animals) and carbon is transferred to them

Plants make carbohydrates(simple sugars like glucose) during photosynthesis

During photosynthesis, plants take carbon from the atmosphere and combines it with water to make carbohydrates(glucose = C₆H₁₂O₆)

When animals eat the plants, they use the carbon in the sugars to build animal tissue

Carbon is passed on from air -> plants -> animals

We send carbon dioxide back to the atmosphere from cellular respiration(AKA breathing)

Cellular respiration breaks down the energy rich carbohydrates(glucose) in every cell and releases carbon dioxide back into the air

Also when we die we have lots of carbon. Bacteria decompose and release carbon into the atmosphere.

But some stuff doesn’t break down !!! 🙁 they form fossil fuels over millions of years

Burning fossil fuels returns carbon dioxide to the atmosphere

If we burn too much fossil fuels, there will be too much carbon in the air that the plants cannot use fast enough -> makes an unbalanced cycle

Water Cycle

• Processes that cycle water through the environment

• Evaporation: Liquid water becomes water vapor. Rises into the atmosphere

• Transpiration: When plants release water from their leaves, also animal sweat

• Condensation: Water vapor turns into liquid water

• Precipitation: Product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds

  • Precipitation falls to the ground and the cycle starts again

Movement of Energy 

Food Chains/ webs- which way energy moves 

• The most common interactions between species of an ecosystem are through feeding relationships

  • These relationships are displayed with food chains & food webs

• Food chain: Illustrates who eats whom

• Food web: A series of interconnecting food chains

• Trophic Levels: Feeding level

  • Describes the position of an organism in a food chain 

    • 1st trophic level - Producer

    • 2nd trophic level - Herbivore (primary consumer)

    • 3rd trophic level - Carnivore or omnivore (secondary consumer)

    • 4th trophic level - Larger carnivore or omnivore (tertiary consumer - Can be apex predator in a smaller ecosystem)

    • 5th trophic level - Top carnivore (quaternary consumer - Apex Predator in larger ecosystems; this level does not exist in smaller ones. There can also be an omnivore at this level but it is very, very rare)

  • The energy level drops as the trophic level increases. 

• Energy Transfer in Food Chains

  • Starts off at 100% at the 1st trophic level, loses 90% per trophic level (keeps 10%)

  • All organisms continually use and release energy to their environment (some is lost as heat energy) 

  • Energy is used and lost at all trophic levels

  • The higher the trophic level, the less energy an organism receives 

    • This is why organisms higher up need to eat more to get sufficient energy  

  • Food chains do not exist in nature; they are used to show simple feeding relationships

• Food Webs

  • Complex food webs are more stable than simple food webs

  • Large numbers of interactions reduces a species’ vulnerability to extinctions or decline

  • Food webs help us anticipate what will happen when a species is removed from or added to an ecosystem

Analyze food web (example: if one specific species is taken away, how does it affect the other ones?) 

• All species in a food web play an important role

• If even one species is taken away, the entire food web may collapse

  • The predators that prey on that species may die out, due to the lack of food

  • The prey that the species usually use for food may start to overpopulate, causing an imbalance in the ecosystem

  • This will eventually affect all trophic levels of the food web 

    • Higher → the lack of prey populations will cause consumers at each higher trophic level to run out of food too, and so on

    • Lower → now that there is an overpopulation of the species’ prey, the lower trophic levels will be overhunted (face more predatory pressure), lowering their population

Feeding levels (trophic levels). Which trophic level receives the LEAST amount of energy? Explain why. Link this to the NUMBER of organisms in the apex predator trophic level.  

• The highest trophic level (the top carnivores/quaternary consumers receives the least amount of energy due to the nature of energy flow through an ecosystem 

  • As energy moves up the food chain (from producers to consumers), a significant amount is lost at each trophic level

    • Approx. 90% is lost, with only about 10% being transferred to the next level

    • This due to the loss of energy through heat, as well as incomplete digestion and natural animal deaths (where the animal is not eaten by a consumer) 

  • Since apex predators are at the top of the food chain, they are at the highest level of the energy pyramid  👋

  • Apex predators often have high energy demands due to their size (requires more energy to maintain)

    • Therefore, their needs for a large and consistent supply of prey for energy + limited availability of prey in the ecosystem = controlled (often few) number of organisms at the apex level 

Feeding roles (herbivore, carnivore, etc) 

• A key feature of any ecosystem is the feeding roles of each species

• Producers: photosynthesise to create chemical energy (plants)

• Consumers: obtain energy by eating other organisms

  • Types of consumers:

    • Herbivore: Animal that eats plants or other producers

    • Carnivore: Animal that eats other animals

    • Omnivore: Animal that eats both plants and animals

    • Scavenger: Animal that feeds on the remains of another organism

• Decomposers: Break down dead organisms and plants

  • Breaks down food externally

  • Consume nutrients on an molecular level

  • Return nutrients to the soil

  • Eg. fungi and bacteria

• Detritivores: Type of decomposer

  • Consume material in large amounts and excretes nutrients

  • Eg. worms, millipedes, slugs, crabs

Energy pyramids (Biomass and numbers too)

Ecological Pyramids 

• Displays relationships between trophic levels in ecosystems

• 3 types:

  • Energy

  • Numbers

  • Biomass

• Energy Pyramids

  • Illustrates energy loss and energy transfer between trophic levels

    • Each time energy is used in the bodies of living things and some of it is released to the environment as heat energy

  • When energy that began as food or sunlight moves through a food chain, organisms use some of that energy for motion, stored in tissues, body heat and other activities

  • The AMOUNT of available energy is less for each population higher up in the food chain

  • Only the energy stored in the tissues is available to the next animal that eats it

    • Therefore, in an ENERGY pyramid…

      • Only a small portion of total energy at any given trophic level (about 10%) is passed on to the next trophic level

      • The size of each layer represents the amount of energy available at that trophic level

Because species in higher trophic levels receive less energy, their population tends to be smaller than the population of species in trophic levels below them

• This is why an ecosystem will have fewer predators (ie. hawks) than herbivores (ie. mice)

• Pyramid of Numbers 

  • Shows the total number of organisms in each trophic level

  • Can be different shapes depending on the food web you are analyzing 

*Regardless of species populations are combined

• Pyramid of Biomass

  • The total mass of all organisms combined within a trophic level

  • Tells us the mass of organisms in a given ecosystem/area

  • Biomass (the amount of matter in a particle or object)

Generally measured in mg/g/kg or lbs

Pyramids Summary 

• Energy pyramids will always be big on the bottom and skinny at the top (loses energy as it goes up)

• Pyramids of numbers and biomass may not have a typical pyramid shape (may have multiple different shapes)

• In a forest ecosystem, the tiny plant-feeding insects (see 2nd trophic level) outnumber the trees they feed on in the first trophic level

• HOWEVER…

  • the biomass of all trees is much greater than the biomass of the insect herbivores that feed on it

Interactions in ecosystems 

Ecosystem interactions 

• In an ecosystem, many interactions happen all the time

  • For example, producers use the Sun’s energy to produce carbohydrates (glucose) and take in water and nutrients from the soil 

  • Predators hunt and eat their prey

    • This reduces prey population

    • Also makes the prey population healthier because it is usually the weakest prey that gets hunted by the predators first (survival of the fittest) 

  • Parents pass down traits to their offspring (genetic!) 

  • Indigenous Beliefs

    • Indigenous populations refer to these interactions as “connections”

      • These connections mean that when something changes in an ecosystem, the changes will affect other parts of an ecosystem

      • E.g., drought → plants dying → primary consumers dying

Limiting factors (biotic vs abiotic). Which ones are density dependent? 

• Various biotic and abiotic factors cause populations to increase or decrease

• Without any limits, populations would grow very quickly

  • 10 breeding pairs of rabbits could expand to 10 million breeding pairs in only 3 years

  • Without any limits, populations of various species would get too large 

• In a healthy, properly functioning ecosystem, limiting factors prevent overpopulation from happening

• Abiotic limiting factors include:

  • Amount of sunlight, water, soil, natural disturbances such as storms, fires, and droughts, and human disturbances such as logging

• Biotic limiting factors include: 

  • Competition among organisms for resources, presence of predators, reliance on other organisms for survival, and the presence of disease causing organisms. 

Tolerance range vs optimal range of abiotic factors 

• All species can survive within a range of abiotic factors

  • This is called the tolerance range of the species

  • Populations will be high within optimal range

  • Populations will be low outside the optimal range but within tolerance range

  • The species will NOT EXIST outside tolerance range

  • Example → Precipitation

• Species with broader tolerance ranges can adapt to a larger variety of conditions and are better suited to acting as an invasive species ! 

• Terrestrial (land) abiotic factors include:

  • Temperature

  • Precipitation

  • Nutrient availability

  • Light

• Aquatic (water) abiotic factors include:

  • Salinity

  • Temperature

  • Acidity

  • Light penetration

  • availability of oxygen and nutrients.

What is an invasive species? 

• A non-native species that causes harm to the ecosystem into which it was introduced

  • These species tend to outcompete native species because they have no natural predators or they reproduce faster compared to native species

  • The population increase of invasive species is correlated with the population decrease of native species

• Example: Dog-strangling vine 

  • Native to Eurasia and introduced to North America as a garden plant

  • Invaded hillsides and ravines in Southern Ontario

  • Grows dense and smothers small plants, tree seedlings, small shrubs, etc.

  • Monarch butterflies lay their eggs on the vine and the larvae do not survive because it is NOT a suitable food source 

Biotic interactions- competition, predation, symbiosis  

• Competition

  • Interaction between two or more organisms competing for the same resource in a given habitat

  • Members of different species may also compete for resources

    • Racoons and ravens may try and feed on eggs from the same nest of a common tree

  • For similar species to coexist in an area, they must have slightly different niches

    • Different species of similar birds can feed off of the same worm, but each species feeds in a different part of the tree

• Predation 

  • Occurs when one organism eats another organism to obtain food

  • Prey animals are well adapted to avoid being eaten – a deer can usually outrun a bear, some animals use camouflage, tasting repulsive, etc. 

  • Some species use mimicry to avoid predators 

    • Mimicry is when a species changes to look like another species

• Symbiosis

  • A close interaction between two different species in which members of one species live in, on, or near members of another species

  • Three mains types of symbiosis: 

  • Mutualism

    • Both species benefit from the symbiotic partnership

      • The leaf cutter ant has a mutualistic relationship with a certain species of fungus

        • The fungus grows in the ant’s colony in which they provide the fungus with food while the ants can eat certain parts of the fungus

  • Commensalism

    • Occurs when one species benefits from a relationship with another species without any harm or benefit to the other species

      • A bird building a nest on a tree

        • The nest does not harm or help the tree, but the bird benefits from this relationship

  • Parasitism 

    • Occurs when one species benefits at the expense of another species 

      • Example: Parasites live on or inside the host and obtain some or all of their nutrition from the host

        • Ticks live on the bodies of mammals and feed on the host’s blood

        • Anopheles mosquitoes transmit the disease malaria from one human to another

Characteristics of populations- carrying capacity  

• As a population grows, each individual gets a smaller share of the resources in the area

• When this happens, organisms in that area get stressed – some die, while others are not able to reproduce

• Eventually, the number of births = the number of deaths and the population reaches equilibrium

• The numbers of individuals stays the same over time

In this picture below, you can see that after a while, the population size does not change

• The habitat has reached its carrying capacity

• This is the maximum number of individuals that a specific environment can support, given the food, habitat, water, and other resources available 

• hout reducing its ability to support future generations of the same species

For an ecosystem to be sustainable, none of the populations in the community can exceed carrying capacity

Human Uses and Assessment of Ecosystems 

Sustainable use 

• Using an ecosystem’s resources in a way that meets our needs without compromising the ability of future generations to meet their needs

- Biodiversity vs Genetic Diversity 

- Biodiversity is the number of different species types in an area / variety of ecosystems on Earth

- Genetic diversity is the differences between individuals of the same species. Less diversity can lead to extinction (spread of diseases), so it is important to have some genetic diversity

- 5 causes of biodiversity decreasing (habitat change, overexploitation, invasive species, climate change, pollution) 

- Habitat change is the process by which humans alter a habitat enough so that the native species can no longer live there (they either die or immigrate)

- Humans clear land for agriculture, forestry, or urban development

- Overexploitation is using resources faster than they can be replaced (leads to extinction)

- Overfishing is an example of overexploitation

- Cod used to be abundant, but overtime, more cod was caught as we invented more advanced fishing technologies

- As a result, we needed to go deeper and we ended up catching younger fish that were supposed to be next years harvest, resulting in less fish

- Overuse of water

- Canada has the world’s largest supply of freshwater

- A drop in water level would affect the ecosystem as there would be fewer fish resulting in less commercial fishing

- Invasive species are non-native species that cause harm to the ecosystem in which it is introduced

- These species tend to outcompete native species because they have no natural predators in this ecosystem or because they reproduce faster compared to native species

- The dog-strangling vine is native to Eurasia and was introduced to North America as a garden plant

- It invaded hillsides and ravines in South Ontario

- Grows dense and smothers small plants, tree seedlings, small shrubs, and etc. 

- Monarch butterflies lay their eggs here and the larvae do not survive

- Climate change is a cause of loss of biodiversity

- When climate change occurs, species need to adapt to it

- Climate change is now driven by global warming caused by humans

- Pollution, more specifically water pollution, is a cause of a decrease in biodiversity

- Bad stuff enters water, things that rely on the water get sick or die

Agroecosystems- what are they? 

• Agroecosystems are complex systems in which many species interact with strong interactions between ecological and management processes

  • Contributes to habitat loss, dramatically alters food webs, supports little biodiversity, and alters biogeochemical and water cycles

  • Includes things like agriculture and pests

    • Agriculture is the art and science of cultivating the soil, growing crops, and raising livestock

    • Many individual species are planted in a monoculture

      • To maximize yields, pests are eliminated

      • However, farmers create the ideal conditions for pests

Pesticides ( what they are, how they work, issues, benefits) 

• Pesticides are a substance used to kill a pest (includes herbicides, insecticides, fungicides, and rodenticides)

• Pesticides obtained from natural sources are effective for shorter periods of time

• Pesticides vary in the number of species they can control

• Broad-spectrum pesticides are pesticides that are toxic to a wide range of species

• Narrow-spectrum pesticides are pesticides that are toxic to a limited number of species 

• Pesticides cause physical or biological harm to pests

  • Diatomaceous earth is a natural product made from the fossilized remains of a type of algae called diatoms and it is an abrasive powder that scratches the waxy outer coating of some insects causing them to dehydrate

  • Pesticides can also interfere with biological processes like photosynthesis or may cause damage to vital organs

• Benefits of pesticides include increasing food production and the reduction in the spread of diseases

• Pesticides are often applied through aerosols of sprays and some of the pesticide never reaches the target because it is carried away from it by the air or the land (on the soil) which causes ecological problems and environmental damages

  • Some ecological costs of pesticide use includes soil, air, and water pollution and how it harms the non-target species

Target/ non target species 

• Target species are the species that you are trying to kill

• Pesticides may accidentally kill non-damaging or beneficial organisms

  • This causes farmers to become more dependent on pesticide use

  • For example, spraying insecticides at the wrong time of the year can kill honey bees, which are essential for pollinating fruit crops

Bioaccumulation vs bioamplification  

• Bioaccumulation is the concentration of a substance like a pesticide in the body of an organism

  • Pesticides that bioaccumulate cannot easily be excreted from the body of an organism (they are not water-soluble, but fat-soluble)

• Bioamplification refers to how the concentration of pesticides increases as you move up the food chain (stored toxins in fats and oils of organisms at one trophic level will be passed on to the next trophic level)

Pesticide resistance 

• Long term use of pesticides can cause some pest species to become resistant to the pesticide (as a result, the pesticide can no longer control the pest)

• The greater the resistance, the more likely the species will survive an application of the pesticide

  • Those that do survive will reproduce and pass on their resistance to their offspring

  • After many generations, the population can become highly resistant to a particular pesticide

• Pests like weeds and insects are likely to develop a resistance because they reproduce frequently

  • To combat this, farmers either apply a greater concentration of the pesticide to have the same effect or they switch to a different pesticide

    • This costs more money and manages the environment (bad cycle)

Organic farming ( IPM) 

• An alternative type of agriculture is organic farming which uses no synthetic pesticides or fertilizers

• Organic farmers may lose crops to naturally occurring pests but the losses may be offset by higher selling prices for organic products and savings (from not purchasing synthetic chemicals) 

• Organic farmers rely on several ecologically sustainable techniques 

Water Pollution, sources 

• Water Pollution: Any physical change in surface water or groundwater that can harm living things

  • There are biological, chemical and physical forms of water pollution

  • Since water is essential for life as we know it, any contamination of our freshwater supply is potentially harmful to living things

  • Pollution…

    • Produces unpleasant odours

    • Makes waters unfit to swim in

    • Sickens and kills aquatic organisms (and those that feed on them)

• Sources of pollution

  • Point Source Pollution

    • Enters a body of water at a specific place (identifiable)

    • Ex: Oil spills from tankers, wastewater from pulp and paper mills, partially treated water from sewage treatment plants 

  • Non-Point Source Pollution 

    • Enters bodies of water indirectly when water from rain or snow travels over land and picks up pollutants from many different sources before entering a stream/lake

    • Ex: Fertilizer and pesticide run-off run farms and salt run-off from roads 

Indicators of water pollution  

• Water quality is defined by its intended use:

  • Water too polluted to drink – acceptable for industrial processes or watering lawns

  • Water too polluted to swim in  – acceptable for boating or fishing

• Two main indicators of water quality

  • Bacteria count

  • Concentration of dissolved oxygen 

Pollutants , sources, and effects