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Grade 7 Science NOTES
Unit 1: Interactions Within Ecosystems
Name:_________________
Chapter 1: An ecosystem is all the living and non-living things in a particular place.
Biotic: the living things and once living things (dead) in the environment such as humans,
trees or fish.
Abiotic: the non-living things in the environment such as water, soil or air.
Biologist: a scientist who studies living things (organisms).
Ecologist: a scientist who studies groups of individuals of the same species that live
together in one ecosystem at the same time (populations).
Organism: any living thing, such as a plant or an animal.
Species: a group of organisms that can successfully mate with each other and reproduce.
Ex: mosquito mates with another mosquito but not a dragonfly.
Adaptation: a characteristic that is inherited and that helps an organism survive in its
environment. Ex: ducks webbed feet.
Habitat: the place in which an organism lives.
Ecosystems: all the interacting organisms (biotic) that live in an environment,
as well as the non-living (abiotic) parts of the environment that affect the organisms.
Ecosystems vary in size from huge oceans to a rotting log.
Habitat vs. Ecosystem:
A habitat is the area where an organism lives whereas an ecosystem is the interactions
between organisms and their habitat.
Biotic (living or dead) Examples
Abiotic (non-living) Examples
rose, cow, spider, mushroom, strawberry
rain, sun, rock, pavement, soil
Population: a group of organisms of the same species, living together in one ecosystem.
Community: a group made up of all the interacting populations that live in an area.
Niche: the role that is undertaken by an organism in an ecosystem; one organism may fill
several different niches. The role of a species includes where it lives, how it obtains its
food, and how it affects its environment. Ex: a “job” or its role in the community,
dragonflies catch mosquitoes while mosquitoes feed on blood.
Level of Organization: Individual (one caribou), Population (two caribou), Community (two
caribou and a tree =all biotic), Ecosystem (two caribou, tree and water =biotic and abiotic)
Four Ecosystems in Atlantic Canada:
1. Coastlines and Oceans:
-tuckamore: clumps of weather-beaten conifers (spruce, fir, pine and larch)
from cold, salty winds of the ocean.
-organisms: seaweeds, barnacles, mussels, starfish, rock crabs, cod, seals, whales, jellyfish.
-below 100 to 200m of water there is no sunlight and only some types of bacteria and animals
can live below these depths.
2. Freshwater Ecosystems: Rivers, Lakes and Ponds:
-lakes occupy more than 8% of land in NL.
-soil and rock determine how muddy or clear the water is.
-organisms: sticklebacks, beavers, ducks, snails, insects, various water plants.
3. Arctic:
-northernmost tip of Labrador
-very low temperatures, little precipitation......cold desert.
-long nights and short days
-permafrost: soil that has been at or below the freezing point of water (0C) for two or
more years. Located a meter below the surface on the tip of Labrador.
-organisms: no trees but have low shrubs, mosses, lichens, caribou, wolves, arctic hares.
4. Forests:
-cover much of NL and poor drainage results in bogs and marshes
-summers are cool and winters are wet
-organisms: balsam fir, white birch, black spruce, mountain ash, moose, caribou, black bear.
-peat: when dead plant material in bogs and marshes decays very slowly as a result of being
covered with water, it builds up over time to produce peat.
-blanket bogs: extensive wetlands.
Range of tolerance:
-the range of abiotic conditions within which an organism can survive.
-treeline: the altitude at which tree growth is impossible.
-struggle zone: trees become fewer and shorter as conditions become less hospitable.
Abiotic Influences:
1. Light and Light Intensity:
-all plants and algae need light to survive. If there is an environment with no light, like deep
in the ocean, no plants will live there. Many animals survive well without light. Ex: bats
-photosynthesis: Plants produce food and oxygen through photosynthesis:
water + carbon dioxide ---sun’s energy—> food + oxygen
-migrate: to go to another place to live when the seasons change.
2. Temperature:
-many reptiles (ex: northern alligator lizard), amphibians, fish and insects rely on the
sunlight to raise their body temperatures and allow them to become active.
3. Soil:
-biotic parts of soil: dead plants and animals with the solids and liquids they release. This
provides nutrients.
-abiotic parts of soil: small rock particles, air and water.
4. Air and Wind:
-BOTH animals and plants use oxygen from the air for respiration.
-cellular respiration for animals: oxygen + food ----energy—> carbon dioxide + water
-some organisms use the air for flight and seed dispersal. Air is made up of mainly nitrogen
(78%), then oxygen (21%), carbon dioxide + water vapour + helium + argon + etc (1%)
5. Water:
-all organisms require water
-water affects the weather and climate and ice provides hunting grounds for polar bears.
Examples of interactions between abiotic and biotic factors in an ecosystem:
1.
Sunlight evaporates water (abiotic-abiotic)
2.
Insects eat plants (biotic-biotic)
3.
Worms aerate (add air) soil (biotic-abiotic)
Chapter 2: Living and non-living things interact in ecosystems
Symbiosis or Symbiotic Relationships:
-A biological relationship in which two species live closely together in a relationship that
lasts over time.
-Three types: parasitism, mutualism, commensalism
Parasitism:  
-A symbiotic relationship between two different types of organisms, in which one partner
BENEFITS and the other partner, is HARMED.
-Parasite: the organism that obtains its food from its partner, ex: tapeworm or tick. They
usually do NOT kill their host but may shorten their life span (ex: roundworms in caribou in
1990s). Some plants are parasites like the mistletoe attaches to a tree and uses a root-like
structure to gain nourishment from the tree.
-Host: the organism that provides the food for the parasite, ex: bear or cat.
-External parasites: Ticks, fleas and lice live on the SURFACE of their hosts. May stay a
SHORT time to feed and reproduce.
-Internal parasites: Tapeworms and roundworms live inside the bodies of their host. May
stay a LONG time...its entire life.
Mutualism:  
-a symbiotic relationship between two different types of organisms, in which BOTH partners
BENEFIT.
-Termites and insects have micro-organisms in their guts that help them digest dead wood by
changing the wood into sugar that provides nourishment for both the termite and the
micro-organism. The micro-organism is provided a warm, safe environment.
-Lichens are made up of algae and fungi living together. The algae provide the food and the
fungi provide the protection by using its threads to anchor the lichen to rocks and helps hold
in water.
Commensalism: 

-A symbiotic relationship between two different types of organisms, in which, one partner
BENEFITS and the other organism appears to NEITHER gain or lose from the relationship.
-clown fish and the sea anemone: The clown fish swims among the poisonous stinging tentacles
of an anemone and is in fact provided with food scraps and shelter since the anemone does
NOT sting the clown fish.
-barnacles and a whale: Barnacles attach to whales gaining shelter and the whale neither gains
nor is harmed.
Predators: organisms that hunt and kill their food.
Prey: organisms that are hunted and killed for food.
Herbivores: animals that eat only plants.
Ex: moose, hares, grasshopper
Carnivores: animals that eat other animals. Ex: wolves, hawks, owls, spiders, shark
Omnivores: animals that eat both plants and animals. Ex: bears, chickens
Consumers: organisms that eat other organisms and the food made by producers.
Can be an herbivore, carnivore or omnivore
Producers: organisms that make their own food rather than eating other organisms to
obtain food. Example: plants using photosynthesis.
Scavengers: organisms that eat decaying plant or animal matter.
Examples: vultures, dung beetles, houseflies, crows, some species of gulls
Decomposers: organisms that break down (decompose) dead or waste materials, such as
rotting wood, dead animals or animal waste.
-they do NOT eat the food as scavengers do but decomposers release chemicals that break
apart dead tissues and cells which they absorb these nutrients into their own cells.
-many species of microscopic bacteria and fungi
Preventing the Growth of Micro-organisms in Food:
-wash your hands, clean counter top, use clean utensils
-keep food well covered or in a sealed container
-canning and vacuum packing keep the air out
-freezing keeps out warmth and removes moisture and freeze-drying removes moisture
-radiation kills micro-organisms
-salting draws the moisture from cells and pickling (use vinegar or strong salt solution called
brine)
Fermentation:
-latin for “to foam or rise by bubbling”
-the process where yeast cells feed on sugary food, breaking down the sugars and producing
alcohol and carbon dioxide gas.
-used to make beer, wine, cheeses, pickled vegetables and some sausages.
Food Chain: model that show how food energy passes from organism to organism.
-first link all food chains begin with a producer (green plants, algae and some
micro-organisms)
-second link consists of consumers that eat producers (herbivores or primary consumers)
-third link has consumers that eat other consumers (carnivores or secondary consumers)
-food chains may have four or more links where the higher links are filled by the secondary
consumers.
-the energy flows from the producers to the consumers and from the herbivores to the
carnivores. The arrows shows the energy flow.
-Example: Daisy  Ladybug  Grouse  Wolf
1st link
2nd link
3rd link
4th link
(producer) (herbivore) (consumer) (consumer)
Food Web: networks of interconnected food chains in an ecosystem
-most consumers eat and are eaten by more than one type of organism.
Energy Transfer:
-fat contains stored energy and other energy is used for life functions such as respiration,
growth and movement. This energy passes out of the body as heat or waste gases
-For example: only about 10% of the energy stored in the plants eaten by a moose eventually
becomes stored energy in the moose. 30% for respiration, 10% for tissues and 60% as
waste. Therefore most of the energy is NOT passed on to the next animal in the food chain.
Energy Pyramid: a model that shows how energy is lost at each link in a food chain.
-there is less animals at the top of a food chain than below them because there is less energy
available for them to use.
-Figure 2.20 on page 56.
Nutrients: contained in food, nutrients are used to repair cells and tissues.
-examples: carbon and nitrogen
-producers get nutrients from soil, water and air.
-consumers get nutrients from their food.
-nutrients are re-used
Nutrient Cycle: the processes that move nutrients back and forth between the biotic and
abiotic environment.
-decomposers play an important role by breaking down matter and dead organisms and
releasing nutrients back into the soil, air and water.
Chapter 3: Natural events and human activities cause changes in ecosystems
Succession: The process by which a biological community changes over time.
Pioneer Species: Species that are the first to appear in an area and can establish themselves
with little of no soil and few nutrients. Ex: bacteria, mosses and lichens
Primary Succession: The sequence of changes the starts with bare rock and eventually
develops into a complex community of plants and animals.
Four steps:
1.Lichens grow on bare rock. By producing acids they break down rock and help to form soil.
2. Soil supports mosses and ferns and eventually creates a habitat for small animals.
3. Small organisms eventually die and add more nutrients to the soil making the soils
deeper allowing the growth of grasses and other plants and more species of animals.
4.Taller shrubs create shade, roots slow erosion, more communities of plants and
animal evolve and bushes and trees provide niches.
Climax Community: A diverse group of species that form a stable ecosystem which can
remain relatively unchanged for centuries if there is no disturbance
Secondary Succession:The regrowth of a community in an area that has changed dramatically
after a disturbance such as a fire.
-STEPS: Fire.....sunlight now able to reach the ground....wildflowers grow....then taller
shrubs.....then trees from the seeds left in the soil or by animals..
-regrowth can occur faster in the matter of years rather than hundreds of years.
-Another NL example: flooding can occur as a result of a beaver dam.
Natural Resources: Materials and products found in nature that people use to meet their
basic needs. Examples: water, oil, metals, lumber, fish.
Biodiversity:The range of organisms present in a community or ecosystem.
The effects of human activities on ecosystems:
-construction of roads and buildings and oil drilling, refining and transportation
-mining, logging, farming, dam building, outdoor recreation
-manufacturing and consumption of goods
Endangered: When a species has such a low population it is nearly extinct.
-Loss of habitat is the largest single cause of the decline in populations of wildlife.
Other factors include introduced species, overharvesting and pollution.
-20 species of animals and plants in NL are endangered, threatened or of special concern.
Extinct:When there are no longer any living individuals.
-This loss of a species the entire community is affected.
Native Species:Wild species that have lived in their environment since before humans
settled the land.
-NL: NL black bear, NL lynx, NL pine martin, red fox, muskrat.....
Introduced Species: Species that have spread beyond their natural range into new territory
because of human activity.
-NL: moose, eastern chipmunk, snowshoe hare, deer mouse, Norway rat.....
Renewable Resources: Living natural resources that, after harvesting, can be replaced by
natural processes in a relatively short period of time. Examples: Fish and trees
Sustainable: When resources are replaced by natural processes or human activity at the
same rate as human activity at the same rate as they are used up by humans.
Unsustainable: When resources are used faster than they can be renewed.
Atlantic Cod Fishery:
New fishing technology.....larger, faster fishing vessels, larger nets, process fish on board
the boat, underwater sonar to detect fish.
More demand.....growing demand for protein = 18 nations fishing on the Grand Banks.
Lack of conservation.....over fishing, little limits on quantities and regulations were often
ignored.
Unsustainable harvesting......In 1977, “200 mile limit” introduced. Canadian boats increased
their limits when the other nations were limited. Other nations began fishing on the “nose
and tail of the Grand Banks” where many fish species reproduced. The fish populations
collapsed.
Monoculture: Planting large areas with a single crop.
Pollutants: Substances that cause harm to the air, soil, water or living things.
Examples:
-Pesticides (pass from insects to birds or frogs...up the food chain)
-Fertilizers (wash from farms into waterways and cause excessive growth of water plants).
-waste oil (covers sea birds and they drown or become poisoned when they try to clean
themselves)
-exhaust from vehicles
Acid Rain:Burning fossil fuels produces nitrogen and sulphur which combine with water vapour
to make acid; this falls to the ground as acid rain.
Acidic: pH of 0 to 6.9 (lower the number the stronger the acid, pH 1 stronger than pH of 6)
Neutral : pH of 7
Basic: pH of 7.1 to 14 (higher the number the stronger the base, pH of 14 is stronger than a
pH of 8)
-pH scale 