Unit 2 and 3

Sec. 2.1: Life on Earth

  • Earth is the only planet in our solar system that contains living

    organisms. An organism can live in terrestrial (land) or in aquatic

    (water) areas. Where an organism lives is referred to as its habitat.

  • • The four spheres of Earth are the atmosphere, lithosphere, hydrosphere,

    and biosphere. All these words have their roots in Greek.

  • • Atmosphere: The layer of gases surrounding Earth. It is critical

    to life on Earth. It moderates surface temperatures (prevents it

    from being too hot during the day or too cold at night). Average

    temperature is 15oC; without the atmosphere, it would be -18oC.

    It also blocks most of the U.V. radiation from the Sun.

    • Lithosphere: The rocky outer shell of Earth. It consists of the

    rocks and minerals that make up the mountains, ocean floors,

    and the rest of Earth’s solid landscape.

    • Hydrosphere: All of the Earth’s water in solid, liquid, and gas

    form. It includes oceans, lakes, ice, rivers, groundwater, and

    clouds. About 97% of Earth’s water is in the oceans.

    • Biosphere: The zone around Earth where life can exist. The

    biosphere is very thin compared to Earth itself. All conditions

    for life must be met and maintained within this

Sec. 2.2: Ecosystems

  • • An ecosystem is all of the living organisms that share a region and

    interact with each other and their non-living environment. An

    ecosystem is composed of both living and non-living components.

    They can be small (like a pond) or large (like a forest).

  • • An ecosystem is composed of both living and non-living components (things).

    Non-living physical and chemical components are abiotic factors (e.g. sunlight,

    temperature, wind, water, minerals). The living components, called biotic

    factors, include all organisms, their remains, and their products or wastes.

  • Ecosystems – Some Common Terms

    • Below are the typical terms related to ecosystems. On the next slide, you will

    see how they are related in a hierarchy of complexity.

    • Species: a group of similar organisms that can reproduce and who's off-spring

    can also reproduce (e.g. moose)

    • Population: all members of the SAME species that can be found in the same

    area (e.g. all the moose in a forest)

    • Community: members of DIFFERENT species that can be found in the same

    area (e.g. moose, bears, squirrels, etc.)

    • Ecosystem: all the living organisms and their physical and chemical

    environment

    • Biome: A large geographical region defined by climate, with a specific set of

    biotic and abiotic features

    • Biosphere: The zone around Earth where life can exist.

    • Sustainability: ability to maintain natural ecological conditions

Sec. 2.4: Energy Flow in Ecosystems

  • • All organisms in an ecosystem require energy.

    The source of almost all energy can be traced

    back to the Sun.

    • The Sun's radiant energy (energy that travels

    through empty space) provides us with

    invisible energy (ex. UV rays) and visible or

    light energy.

    • Almost 70% of the Sun’s radiant energy is

    absorbed by the Earth and converted to

    thermal energy (warms up the atmosphere,

    water, and Earth), 30% is reflected by the

    clouds or Earth’s surface, and a very small

    amount (0.023%) is absorbed by plants.

  • • Many organisms are able to convert light energy

    (from the Sun) into chemical energy using the

    process of photosynthesis. Organisms that make

    their own food (glucose) in this way are called

    producers.

    • Photosynthesis can be represented by the

    following word equation:

    • carbon dioxide + water light energy sugar + oxygen

    • The sugar (glucose) produced can be stored,

    used to form carbohydrates (such as cellulose),

    or converted to starch for long term storage.

  • • To use the sugar (and obtain its stored energy),

    plants perform the complementary reaction

    called cellular respiration:

    • sugar + oxygen → carbon dioxide + water + energy

    • Many organisms cannot photosynthesize. They

    are consumers and must consume other

    organisms for food. Ultimately, consumers must

    undergo cellular respiration to release the usable

    energy from their food.

    • Only producers undergo photosynthesis.

    • Both producers and consumers undergo cellular

    respiration.

    • Photosynthesis and respiration are said to be

    complementary processes. Why?

Sec. 2.5: Food Webs & Ecological Pyramids

ECOLOGICAL NICHES

• The way in which an organism interacts with other species well as

with their environment is called a species’ niche in an ecosystem.

• This is the role or job that species plays in an ecosystem (e.g. what

it feeds on, what eats it, and how it behaves). For example, a great

white shark is a top predator that feeds on seals and large fish.

• No two species occupy identical niches

FEEDING ROLES IN ECOSYSTEMS

• Re-cap from section 2.4:

• Producer: An organism that makes its own food.

• Consumer: An organism that consumes other organisms for food.

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

Consumers can be further sub-divided as follows (Sec. 2.5):

• Herbivore: An animal that eats plants or other producers.

• Omnivore: An animal that eats both plants and animals.

• Carnivore: An animal that eats other animals.

• Scavenger: An animal that feeds on the remains of another

organism.

FOOD CHAINS

• The most common interactions between species are through

feeding relationships. The easiest way to display these

relationships is with a food chain (a sequence of organisms

each feeding on the next, showing how energy is transferred

from one organism to another).

• The position, or “feeding” level of an organism along a food

chain is called a trophic level. Producers (plants) always

occupy the first (lowest) trophic level. Herbivores (also called

primary consumers) occupy the second trophic level.

Omnivores and carnivores occupy the third trophic level or

higher (see next slide for a sample food chain).

• A more accurate way to represent the feeding relationships within a

community is a food web. It shows a series of food chains that are

interconnected.

• Food webs are highly complex, with consumers feeding on many

species. The large number of interactions tends to reduce the

vulnerability of any one species to the loss or decline of another species.

• Food webs are useful tools to figure out what many happen when a

species is removed from or added to an ecosystem.

• Some food webs have very important species called indicator species.

These species are essential to normally functioning food webs and must

be present. If they disappear or change in number, then the food web is

at risk of collapse.

• Another way ecologists illustrate how

ecosystems function is through

ecological pyramids.

• The three types are pyramids of

energy, numbers, and biomass. Each

one has its practical use.

• The diagram on the right is a pyramid

of energy. It shows that about 10% of

the energy available at a trophic level

is transferred to the next trophic level.

This is why there are so few trophic

levels in a food chain or food web.

• The pyramid of energy is the most

accurate depiction of energy transfer.

As a result of energy lost at each

trophic level, those at the top of a food

chain (or web) require a great deal of

organisms to support it. We can first

look at this idea using a pyramid of

numbers. The numbers in this

pyramid are for the entire lifetime of

the top carnivore.

• These pyramids aren’t always direct

measures of the nature of feeding

relationships. If one oak tree is given the

same value as a small weed, the numbers

are an inaccurate way of analyzing

feeding relationships. This is due to the

fact that an oak tree could support a

much larger number of organisms than a

single dandelion.

• To see feeding relationships in an

ecosystem more clearly, we focus on the

biomass (in kg) of the prey and how it

supports a given biomass of a predator in

a food chain. This pyramid of biomass

shows a more accurate version of energy

transfer than a pyramid of numbers.

Sec. 2.6 - Cycling of Matter in Ecosystems

• All life on Earth requires water and nutrients.

• Water and nutrients are composed of physical matter, which

you obtain from food and drink.

• These particles of matter do not stay in your body forever.

Every part of every cell is replaced over time.

• The particles that make up matter cannot be created or

destroyed (Law of Conservation of Mass). It means that all

water and nutrients must be produced or obtained from

chemicals that already exist in the environment.

• This happens in a series of biogeochemical cycles in which

chemicals are continuously consumed, rearranged, stored, and

used. This is unlike energy, which is lost at each trophic level.

The Carbon Cycle

• Carbon moves between the abiotic and biotic parts of an

ecosystem in the carbon cycle. Most of this exchange occurs

between carbon dioxide and photosynthesizing plants and

micro-organisms.

The Carbon Cycle – Carbon Deposits

• While large quantities of carbon are cycled via photosynthesis and

respiration, most of Earth’s carbon is not cycled. Instead, it is

stored as:

• Fossil fuels (e.g. coal, oil) and natural gas; these are the most

valuable (form when decomposed organisms are compressed over

millions of years).

• Limestone (formed from dead marine organisms)

• Plant tissue, and dissolved carbon dioxide in the world’s oceans

(these two are carbon sinks rather than deposits, as carbon can

enter or leave them over relatively short time periods).

• Human activity affects the carbon cycle by increasing the levels of

carbon dioxide in the atmosphere via burning fossil fuels and

deforestation (both affect climate change).

The Nitrogen Cycle

• Nitrogen is extremely abundant in the atmosphere (about 78% of

the air you breathe is nitrogen). However, it is not easy to acquire

nitrogen directly from the abiotic environment.

• Most of the nitrogen used by living things is made possible by

nitrogen-fixing bacteria (found in the soil and on the roots of

certain plants, like clover). They convert nitrogen in the air (N2

)

into a variety of nitrogen-containing compounds (e.g. nitrates).

• Once in the soil, nitrogen-rich compounds (e.g. nitrates) are

absorbed by producers, and passed on to consumers.

• When animal wastes and dead plants & animals are decomposed,

the nitrogen-rich compounds are returned to the soil. The cycle is

complete when denitrifying bacteria convert the compounds back

into nitrogen gas, and release it back to the air.

Sec. 2.7: Biotic & Abiotic Influences on Ecosystems

  • • What determines the size of a population and where a

    particular species can and does live?

    • Ideal biotic and abiotic conditions allow a species to flourish.

    Other conditions may lead to a species’ decline or extinction.

    • Both biotic and abiotic factors determine where a species can live.

    • A limiting factor is any factor that places an upper limit on the

    size of a population. Examples are availability of food (biotic)

    and access to water (abiotic).

    • Human influences often act as limiting factors.

  • Influence of Abiotic Factors

    • Abiotic factors (e.g. temperature, light, soil) can influence a

    species’ ability to survive. Every species is able to survive

    within a range of each of these factors, called the species’

    tolerance range.

    • Near the upper and lower limits of the tolerance range,

    individuals experience stress (reduces health and rates of

    growth and reproduction).

    • The optimal range is the range within which the species is best

    adapted. This produces the largest and healthiest populations.

    • Each species has a tolerance range for every abiotic factor.

  • Influence of Abiotic Factors

    • Some species have wide tolerance

    ranges, while others have much

    narrower ranges. Species with broad

    tolerance ranges tend to be widely

    distributed and may easily invade

    other ecosystems.

    • The distribution of most terrestrial

    plant species is largely limited by a

    combination of temperature,

    precipitation, and light. The black

    spruce tree is limited to regions with

    long, cold winters and moderate

    precipitation (about half of Canada!)

    • The key abiotic factors in aquatic

    ecosystems are salt concentration,

    and the availability of sunlight,

  • Influence of Biotic Factors

    • While abiotic fact0rs determine where a particular species is able

    to live, biotic factors often determine the species’ success. For

    example, while deer are able to survive the abiotic conditions in

    dense forests, they are more abundant in open woodlands (they

    can obtain preferred food and watch for predators).

    • Many key biotic factors involve interactions between individuals.

    The obvious one is competition (e.g. squirrels compete with each

    other for pine cones; birch and maple trees compete for sunlight).

    • The other interactions between species are:

    • Predation, mutualism, commensalism, parasitism.

  • Mutualism

    •Both individuals

    benefit each other.

  • Commensalism

    • One individual benefits and the other neither benefits nor is harmed.

  • Parasitism

    •One individual lives on or in and feeds on a host organism.

  • Predation

    •One individual

    (predator) feeds

    on another (prey).

  • Competition

    •Two individuals vie for the same resource.

  • Carrying Capacity

    • As a population’s size increases, the demand for resources (e.g.

    food, water, shelter) also increases. Eventually, there will not be

    enough resources for each individual.

    • Also, as individuals become more crowded, they become more

    susceptible to predators and diseases. Eventually the population

    reaches its carrying capacity – the upper sustainable limit that the

    ecosystem can support.

    • Carrying capacity can be altered through natural or human activity

    (e.g. irrigation in a desert, loss or introduction of a species,

    hunting).

Sec. 2.8 Major Terrestrial Ecosystems

  • • Earth’s biosphere is home to millions of species. Despite this, there are

    relatively few prominent and easily recognizable types of ecosystems.

    • These prominent types of ecosystems have characteristic features that

    are observable even with identifying individual species.

    • The most important factor in determining the location and makeup of a

    terrestrial ecosystem is climate.

    • On a global scale, the pattern and range of temperature and precipitation

    cause the establishment of ecologically similar, terrestrial regions called

    biomes, which have characteristic biotic and abiotic factors.

    • Canada has 5 major biomes: tundra, boreal forest, mountain forest,

    grassland, and temperate deciduous forest. B.C. has several smaller

    biomes, including a narrow strip of temperate rainforest along the coast.

  • Tundra

    • Biotic factors:

      • Arctic foxes

      • Caribou

      • Musk oxen

      • Lemmings

      • Snowy owls

    • Abiotic factors:

      • Permafrost

      • Low temperatures

      • Short growing season

      • Strong winds

      • Limited precipitation

    • Boreal Forest (Taiga)

      • Boreal forest is the largest terrestrial biome on Earth.

      • It is characterized by cold temperatures and long, harsh winters.

      • Boreal forests are dominated by coniferous trees such as spruce, fir, and pine.

      • Biotic factors in the boreal forest include plants, animals, and microorganisms.

      • Abiotic factors in the boreal forest include temperature, precipitation, soil composition, and sunlight availability.

      • Boreal forests play a crucial role in carbon storage and climate regulation.

      • They provide habitat for a wide range of wildlife species, including migratory birds and large mammals like moose and bears.

      • Boreal forests are important for indigenous communities, providing them with food, medicine, and cultural resources.

      • Human activities such as logging and mining pose significant threats to the boreal forest ecosystem.

      • Climate change is also impacting the boreal forest, leading to changes in species distribution and increased risk of wildfires.

    • Temperate Deciduous Forest

      • Biotic factors:

        • Trees such as oak, maple, and beech

        • Animals like deer, squirrels, and bears

        • Insects including butterflies and beetles

        • Fungi and bacteria

      • Abiotic factors:

        • Temperature variations throughout the year

        • Precipitation levels

        • Soil composition and nutrients

        • Sunlight availability

        • Water sources like rivers and streams

    • Grassland

      • Biotic factors:

        • Grasses

        • Shrubs

        • Trees

        • Herbivores

        • Carnivores

        • Decomposers

      • Abiotic factors:

        • Sunlight

        • Temperature

        • Precipitation

        • Soil composition

        • Wind

        • Fire

    • Mountain Forest

      • Biotic factors:

        • Trees

        • Shrubs

        • Mosses

        • Ferns

        • Birds

        • Mammals

        • Insects

        • Reptiles

        • Amphibians

        • Fungi

      • Abiotic factors:

        • Temperature

        • Precipitation

        • Sunlight

        • Soil composition

        • Altitude

        • Wind patterns

        • Water availability

        • Rock formations

        • Oxygen levels

        • Nutrient availability

Sec. 2.9 Major Aquatic Ecosystems

• Aquatic ecosystems are divided into two broad categories:

• Freshwater ecosystems have salt concentrations that are typically below 1%.

• Ocean (or marine) ecosystems have salt concentrations averaging about 3%.

• While the difference in salt concentrations may appear small, it has a

dramatic influence on the chemical and physical properties of the water.

Freshwater Ecosystems

• Freshwater ecosystems consist of

(1) moving bodies of water (e.g.

rivers, streams) and (2) nearly

stationary bodies of water (e.g.

lakes, ponds).

• Rivers and streams are unique

among ecosystems as they are

continuously flushed with a fresh

supply of water from upstream.

Organisms must either swim

continuously against the current or

attach themselves to the bottom or

some other fixed object.

Freshwater Ecosystems – Lakes and Ponds

• Lakes and ponds are classified based on their nutrient levels:

• Oligotrophic bodies of water are low in nutrients (see next slide). Even

with abundant light (these lakes are deep and clear), photosynthetic

organisms have difficulty obtaining enough nutrients to grow.

• Eutrophic bodies of water are high in nutrients. Photosynthetic

organisms (e.g. plants, algae) grow more rapidly and support a large

biomass of consumers. Eutrophic bodies of water are often clouded with

suspended microscopic plankton.

• Wetlands (e.g. bogs and marshes) are large areas of shallow water or

saturated soils. They are nutrient rich and support a large population of

fish, amphibians (e.g. salamanders), insects, and birds. Wetlands act as

huge sponges and play a critical role in filtering water in the water cycle.

Marsh

- Constantly

flooded with

water from a

specific source

(e.g. river, lake,

ocean, etc.)

- Rich in mineral

deposits

- Plants are mostly

grasses, reeds,

and rushes.

Swamp

- Waterlogged soil

with interspersed

areas of dry land

- Most swamps

develop from

marshes

- Like marshes, are

found on the

edge of rivers,

lakes or oceans

- The defining

characteristic of

swamps is the

abundance

Bog

- A wetland with a

sealed clay

bottom which

prevents water

from seeping out.

- Form when

plants decay in

lakes and fill

them up, forming

peat.

- Lack nutrients

due to slow rate

of decay.

- Mosses, fungi,

small shrubs.

Watersheds

• A watershed is the area of land through which all water drains into a single

river or lake; it is an important characteristic of freshwater ecosystems.

Marine (Ocean) Ecosystems

• More than 70% of the Earth’s surface is covered in ocean. Most of the water

that evaporates into the air and falls as rain and snow (water cycle) comes

from the oceans.

• Marine algae play a critical role in the production of oxygen and the

absorption of carbon dioxide gas from the atmosphere.

• Much of the ocean supports very little life. The open ocean is nutrient poor

and unable to support many photosynthesizing organisms. The deep ocean

is a lightless environment, so photosynthesis is impossible.

• In contrast, the shallow waters near shore are nutrient rich and support

abundant life. Examples are coral reefs, estuaries, and mangroves.

The Intertidal Zone

• Ocean coastlines are ecosystems that are part-time terrestrial and part-time

aquatic. They are home to the unusual communities that occupy the

intertidal zone – the area between the low-tide and high-tide lines.

• Many coastlines exhibit a significant change in water levels about four times

a day, with two periods of high tide interceded by two periods of low tide.

• Among the most common species that inhabit this unusual environment are

seaweeds, barnacles, sea stars, and urchins.

• Many intertidal species have protective body coatings and tough tissues to

withstand the daily pounding of wave action, since they live on the coast.

Sec. 3.2 - Equilibrium and Change

  • • On a large scale, most natural ecosystems are in a state of equilibrium.

    This means that their biotic and abiotic features remain relatively

    constant over time.

    • When ecosystems are in equilibrium, populations are healthy and stable.

    • On the scale of biomes, ecosystems remain relatively unchanged over

    time. This is not true, however, on a small scale. Smaller ecosystems are in

    a constant state of change. A disturbance such as a forest fire or disease

    outbreak can cause short-term changes on a local level.

    • The process of establishing and replacing a community following a

    disturbance is called ecological succession.

  • Ecological Succession

    • Ecological succession is initiated by a disturbance such as a geologic event

    (e.g. volcanic eruption), a fire, or human activity (e.g. deforestation).

    • Primary succession occurs on soil or bare rock, where no life previously

    existed (e.g. following a volcanic eruption).

    • Secondary succession follows a disturbance that disrupts but does not

    destroy the community (e.g. regrowth of an area following a forest fire).

    • Severe pollution events or industrial activity (e.g. surface mining) are

    human-caused disturbances that initiate secondary succession.

    • Succession is a very gradual process, that may take decades (in the case of

    secondary succession) or centuries (primary succession).

  • • Succession provides a mechanism by which ecosystems maintain their

    long-term sustainability. It allows ecosystems to recover from natural or

    human-caused disturbances.

    Sec. 3.3 Biodiversity

    • • The number of species on Earth has been estimated to be over 5 million

      (some biologists say up 50 million) but only 1.5 million species on Earth

      have been studied.

      • Biodiversity (or biological diversity) is the variety of life found in an area.

      If it’s measured, the number of species will represent the species richness.

      • In general, species richness tends to be higher closer to the equator. For

      example, in a Peruvian rainforest, scientists identified 283 tree species in a

      single hectare (1oom x 100m, or 2.47 acres). A similar-sized deciduous

      forest in Ontario would have fewer than 15 tree species.

    • Biodiversity Under Attack

      • Many of Earth’s species are dying out, or going extinct. Their habitats are

      being destroyed through:

      • deforestation

      • urban and agricultural expansion

      • pollution

      • climate change

    • Extinction as a Process

      • Extinction is a natural process. Over millions of years, some species

      become extinct, while new species arise.

      • There have been at least five major extinction events in the past 1 billion

      years. Extinction events are usually caused by a catastrophic event such as

      an asteroid impact or a massive volcanic eruption. Between such rare

      events, extinction rates are very low.

      • Unfortunately, human activity has drastically increased the rate of

      extinction. In the past 400 years, over 700 species of vertebrates have

      become extinct.

      • 12 species have become extinct in Canada in since 1844

    • Species at Risk -Terms

      • The following terms are given to species that are at risk of becoming extinct:

      • Extirpated – can no longer be found in a specifc area

      • Endangered – a species facing imminent extirpation or extinction

      • Threatened – a species likely to become endangered if factors reducing

      its survival are not changed

      • Special Concern – a species that may become threatened or endangered

      because of a combination of factors

Sec. 3.4: Habitat Loss

  • Deforestation leads to habitat loss for many species.

  • Pollution from industrial activities contaminates air, water, and soil.

  • Overfishing disrupts marine food chains and depletes fish populations.

  • Urbanization destroys natural habitats and increases pollution.

  • Climate change alters ecosystems and threatens biodiversity.

  • Agriculture practices, such as pesticide use, can harm ecosystems.

  • Mining activities cause habitat destruction and water pollution.

  • Introduction of invasive species disrupts native ecosystems.

  • Land degradation reduces soil fertility and affects plant growth.

  • Human activities contribute to the extinction of species.

Sec. 3.5: Non-Native Species

• A non-native species is an organism that is introduced to a new

ecosystem, one in which it wasn't naturally found in. This introduction is

usually done by human means (whether unintentional or deliberate).

• This introduction usually fails because this organism is now in an

ecosystem which is outside its tolerable range for abiotic factors.

• However, if this introduction is successful, it can be beneficial, harmful, or

have no effect on its new ecosystem.

The Introduction of Non-Native Species

• A successful introduction may be harmful for the following reasons:

• it competes with native species for food, resources, space

• it damages the balance or equilibrium of an ecosystem (energy or nutrient

cycles)

• its population can't be controlled because it doesn't have any known

predators

• it can cause damage to agriculture, crops, waterways

• can cause diseases and become pests

Invasive Species

• A species that is harmful to its new ecosystem is called an invasive

species. With world traveling and importing and exporting goods more

prevalent in the world today, it is easy to see how the unintentional

introduction of non-native species is common.

• An attempt to control an invasive species can be by chemical, (ex.

pesticides), mechanical, (ex. hunting, trapping) or biological (introduce

another species that doesn't affect the native species) means.

  • Invasive species can cause significant ecological damage

  • They can outcompete native species for resources

  • Invasive species can disrupt food chains and alter ecosystems

  • They can reduce biodiversity and threaten endangered species

  • Invasive species can cause economic losses in agriculture and forestry

  • They can damage infrastructure and property

  • Invasive species can spread diseases to humans, animals, and plants

  • They can negatively impact human health and well-being

  • Invasive species can require costly management and control efforts

  • They can have long-lasting and irreversible effects on ecosystems