Fundamentals of Ecology


2.6 Ecological Pattern of Stratification

Investigating Stratification

Concept 1: Biological Complexity & Species Interactions

Success Criteria & Vocabulary

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  • I can distinguish between biosphere, biome, ecosystem, community, population, and individual.

  • I can give examples of abiotic factors and biotic factors.

Click this drop-down menu to see the list of Vocabulary.

Abiotic factor: Physical conditions in an ecosystem.

Biome: Large geographical areas with similar conditions.

Biosphere: Part of Earth that contains all living organisms.

Biotic factor: Relationships between organisms in an ecosystem.

Browsing: Type of exploitation where an animal eats high-growing plants.

Commensalism: Interrelationship where one species benefits from the relationship, while the host species is unaffected.

Community: All the populations of species in an ecosystem.

Competition: Interrelationship where species/individuals in a contest for the same resources.

Ecology: Study of relationships between organisms and their environment.

Ecosystem: A community of organisms AND physical conditions interacting as a system.

Environment: Combination of factors in an ecosystem (both abiotic and biotic factors).

Exploitation: Interrelationship where one species benefits at the expense of the other.

Individual: Any one organism.

Interspecific competition: Type of competition between individuals from different species.

Intraspecific competition: Type of competition between individuals from the same species.

Mutualism: Interrelationship where both species benefit from the relationship.

Population: Group of organisms of the same species in an ecosystem.

Predation: Type of exploitation where a predator kills the prey.


Video: Biological Complexity & Species Interactions

Species Interactions (Use examples below)

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Examples of Species Interactions

Examples of Species Interactions

Clownfish live in the tentacles of sea anemones. The territorial fish protects the anemone from anemone-eating fish, and in turn the stinging tentacles of the anemone protect the clownfish from its predators. Clownfish may also even discard food scraps to the anemone!

Camouflage is an organism's ability to blend in with its surroundings. This tree frog is camouflaged as it blends in with the surrounding tree bark. It does this to hide from predators or catch prey.

In East African open grasslands, scavengers such as hyenas, vultures, and maribou storks try to get their share of the meat remaining on the carcass of a lion kill.

Gardeners don't like these mint leaf beetles because both adults and their fat black larvae feed on the leaves of mint plants.

Lichens are actually made up of two interacting organisms: a fungus and an algae. The fungus gets its food from sugars made by algae during photosynthesis. In turn, the fungus provides the algae a habitat that protects from UV radiation, drying out, and herbivores.

Kererū have the widest gape of all New Zealand native birds, which allow it to eat large berries like the berries from this karaka tree. In turn, kererū poop out the karaka seeds away from the parent tree.

Oxpecker (also known as tick birds) feed on skin parasites of large herbivores like this Cape buffalo. These birds will act as an early warning system by calling when predators approach.

The Pacific butterfish are immune to the stings of this sea nettle jellyfish . This allows them to be in close proximity to the jellyfish, and get protection from predators.

Bamboo has very little nutritional value, so pandas have to eat 12-38 kg of it a day!

Inside this pitcher plant is liquid that drowns and digests insects that fall in.

Nectar is the normal diet for tui birds. This tui got covered in pollen as it drank the nectar from this flax plant. The tui will spread the pollen to other flax plants it drinks from.

Epiphytes are plants that grow on other trees in search for more light. They do this without harming the host plant. In this picture, several epiphyte species grow on the same tree branch.

A spider has established a web around this gazelle's horns.

Even though termites feed on wood, they can't digest it themselves. Bacteria living inside the termite actually break down the wood, producing by-products that both organisms can digest.

Pilot fish gather around this Oceanic Whitetip shark because they eat parasites on their host and leftovers from their host. In turn, sharks do not eat pilot fish because pilot fish eat their parasites.

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Concept 1: Support Notes

Ecology & Levels of Biological Complexity

ECOLOGY is the study of relationships between organisms and their ENVIRONMENT.

These relationships involve interactions with the physical (ABIOTIC) FACTORS, as well as the interrelationships with other species (BIOTIC FACTORS).

In ecology, living organisms can be studied at different levels of complexity.

  • The BIOSPHERE contains all living organisms.

  • BIOMES are large geographical areas with similar conditions.

  • An ECOSYSTEM is made up of non-living abiotic factors and the community of organisms, which interact as a system.

  • The COMMUNITY is all the populations of different species living and interacting in an ecosystem.

  • A POPULATION is a group of organisms of the same species in an ecosystem.

  • An INDIVIDUAL is any one organism.

Example: Biosphere contains all plants and animals like elephants and the grass that is in this picture, as well as all other living organisms we cannot see with the naked eye, like bacteria.

Example: This is an oceanic biome.

Example (to the right): An African savanna ECOSYSTEM made up of non-living ABIOTIC FACTORS like sunlight, wind, air temperature, humidity. In the soil, there are factors like nutrient availability, soil moisture, pH. In the water, there are factors like dissolved nutrients, dissolved oxygen, pH and temperature.

In this ecosystem, there is a COMMUNITY of different POPULATIONS of living organisms. There is a population of lions, rhinos, gazelles, eagles, fish, and don’t forget the plant populations the tree and seaweed that make up the community of organisms.

These INDIVIDUALS interact with one another, and these interactions are called BIOTIC FACTOFS - these organisms are either competitors, predators, they may work together and so on.

The Different Types of Species Interactions

No individual organism exists in isolation. Each organism interacts with other organisms. These species interactions are really important in determining the community structure and composition.


MUTUALISM is the type of species interaction where both species benefit from the relationship.

Example: The bee collects nectar from mānuka flowers and turns this into honey to feed bee larvae. The mānuka flowers get cross-pollinated by bees, resulting sexual reproduction.


COMMENSALISM is the type of species interaction where one species benefits, and the other species doesn’t benefit or get harmed from the interaction.

Example: Epiphytes are types of plants that grow on another plant, to access a better position in the forest, and therefore more sunlight. They do not harm nor benefit the host plant.

Exploitation: Predation & Herbivory

EXPLOITATION is the type of interaction between species, where one species benefits at the expense of the other. For this standard, there are two types of exploitation you must know about: PREDATION and HERBIVORY.

Predation is where the predator kills the prey. Example: Gannet chick kills and eats fish.

Herbivory is where the herbivore/omnivore eats parts of the plant but does not kill it. Example: Possums browse on red mistletoe flowers and leaves but does not kill the entire plant.

By the way, GRAZING and BROWSING are two different types of herbivory - They are NOT the same thing!


COMPETITION is the type of interaction between species or individuals where they compete for the same resources. As a result of this competition, both species or individuals are usually harmed. There are two types of competition: INTRASPECIFIC COMPETITION, and INTERSPECIFIC COMPETITION.

Intraspecific Competition

Intraspecific competition is competition between individuals from the SAME species.

Example: Kahikatea seedlings are competing for the same resources (light, and water and nutrients from the soil). It is likely that one seedling will out-compete the rest to grow into a kahikatea tree.

Interspecific Competition

Interspecific competition is competition between individuals from DIFFERENT species.

Example: The kea and possum are of different species, but they compete for red mistletoe flowers for food.

Concept 2: Adaptations, Ecological Niche, & Gause's Principle

Success Criteria & Vocabulary

Click this drop-down menu to see the Success Criteria.

  • I can describe the three types of adaptations using examples.

  • I can describe ecological niche in terms of habitat and adaptations using examples.

Click this drop-down menu to see the list of Vocabulary.

Abiotic factor: Physical conditions in an ecosystem.

Adaptation: Any inherited trait that helps an organism survive in its habitat.

Behavioural adaptation: Activities or actions an organism does to help it survive in its habitat (type of adaptation).

Competition: Interrelationship where species/individuals compete for the same resources.

Ecological niche: Functional position of an organism in its environment; way in which organisms survive in their environment.

Gause's competitive exclusion principle: Two different species CANNOT occupy the same ecological niche in a habitat and coexist stably.

Habitat: Place in which an organism lives.

Physiological adaptation: Internal processes in an organism that help it survive in its habitat (type of adaptation).

Structural adaptation: Physical traits that help an organism survive in its habitat (type of adaptation).


Video: Adaptations, Ecological Niche & Gause's Principle

Adaptations & Ecological Niche

(Work on your copy on Google Classroom).
2.6 Concept 2: Adaptations & Ecological Niche

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Concept 2: Support Notes

What is a Habitat?

Before you can learn the concept of ECOLOGICAL NICHE, you must first understand what a HABITAT is and what an ADAPTATION is.

A habitat is the place in which an individual organism lives. And this habitat is influenced by ABIOTIC FACTORS such as temperature, humidity, rainfall, and so on.

For example: Northland brown kiwis can be found inhabiting dense rainforests in damp gullies, which are large ditches or small valleys carved out by water. Kiwis rely on their habitat being damp and the soil being moist because they feed on earthworms which are found in these damp and moist environments.

Types of Adaptations

An ADAPTATION is an inherited trait or feature that helps an organism survive in its HABITAT. It allows the organism to access the resources in its habitat, and withstand the ABIOTIC FACTORS in that habitat.

There are three types of adaptation: STRUCTURAL, BEHAVIOURAL, and PHYSIOLOGICAL.

Structural Adaptations

Structural adaptations are physical traits that help an organism survive.

Example: Pukatea trees are known for their large and wide buttress roots that physically anchor the tree, allowing it to grow up to 40 metres!

Behavioural Adaptations

Behavioural adaptations are activities or actions an organism does to help it survive in its habitat.

Example: Skinks are cold-blooded, which means they have to go out and bask in the sun to increase their body temperature.

Physiological Adaptations

Physiological adaptations are internal processes in an organism that help it survive.

Example: The cells of venus fly trap plants make pheromones (chemicals that attract insects), that lure insects in.

Ecological Niche

An ECOLOGICAL NICHE describes the functional position of an organism in its environment, which is comprised of its HABITAT and the resources it obtains from its habitat.

To be able to withstand ABIOTIC FACTORS in its habitat and obtain the resources such as food from its habitat, the organism needs to have certain ADAPTATIONS. It is the adaptations that give an organism its ‘functional position’ in its environment.

When considering the ecological niche of an animal, think about the following questions:

  • How does the organism survive in this environment?

  • When is it active?

  • What does it eat?

  • How does it get its food?

  • Does it have any threats or predators?

  • How does it avoid these threats or predators?

  • What abiotic factors does it have to withstand?

  • How is it adapted to withstand these abiotic factors?

To the right is a diagram to help you understand 'ecological niche', using the example of a possum.

Gause's Competitive Exclusion Principle

When two different species that have very similar ecological niches are brought into direct competition, one will benefit at the expense of the other - the species that doesn’t benefit gets excluded, they’re forced out.

GAUSE'S PRINCIPLE states that: "Two different species cannot occupy the same ecological niche in a habitat and stably coexist."

Two species with the same NICHE will directly COMPETE for the same resources. One species will outcompete the other.

That’s because species with exactly identical niches also have exactly identical needs, which means they would directly compete for precisely the same resources. They would be directly competing for the same food, the same nesting sites. If this happens, one species will outcompete the other species for these resources, and cause the extinction of the weaker species.

Example of Gause's Principle: Paramecium

A good example of Gause’s Competitive Exclusion Principle is the interaction between two unicellular organisms (that’s an organism that’s made up of just one cell, so they’re incredibly small).

When paramecium aurelia and paramecium caudatum are grown separately in the laboratory, so they’re occupying different habitats, they both thrive. We can see that the number of paramecium aurelia cells increase as time goes on, and the same goes for the number of paramecium caudatum cells.

But when the two species of paramecium are grown in the same habitat, in the same test tube, the number of paramecium aurelia cells in green increases in numbers while the number of paramecium caudatum in purple decreases until there is none left. When they’re put in the same habitat, the two different species were directly competing for space and food. This intense competition harmed both species, but eventually one out-competed the other to extinction. This is Gause’s Competitive Exclusion Principle.

Example of Gause's Principle: Moth Caterpillars

There are two species of moth caterpillars that feed on the harakeke (flax) leaf. Both moth caterpillars are sensitive to light and are therefore nocturnal. They eat at night and shelter during the day in rolled up dead leaves and debris. Both species are native to New Zealand. They do not kill the harakeke on which they graze, however they are considered a pest by flax weavers.

Interestingly, they cannot withstand prolonged immersion in water. So when harakeke grew naturally along rivers and in wetlands became exposed to flooding, a great number these pests were destroyed.

There are three species of wasp that help control the numbers of both moth caterpillars (Paniscus productus, Phorocera marginata, and Syrphus ropalus). An adult wasp lays injects its eggs inside the moth caterpillar (host). The host lives while the eggs hatch into larvae and until the parasitic larvae are almost ready to emerge and become pupae (stage between larvae and adult). When this time comes, the host ceases feeding and becomes very sluggish, seeming to be incapable of much movement. Once the parasitic larvae emerge, they become pupae. Very often the host moth caterpillar is quite helpless for several days before death. After the emergence of parasites, the host caterpillar is dry and reduced to empty skin.

Window Moth Caterpillar (Orthoclydon praefactata)

The harakeke window moth caterpillar feeds nocturnally on the under surface of young harakeke leaves. To do this, it has jaws (structural adaptation) that scrape the underside of the leaf, leaving the top colourless. This 'scraping' exposes the harakeke fibres, which soon decays. In older leaves, the window often breaks, leaving a hole.

Window moth caterpillars are physically unable to eat flax/create a window right to the edge of the leaf.

Window moth caterpillars are green at first, then later turn pale yellow with red stripes (not pictured) before turning into an adult moth (pictured). This completion of their life cycle is called metamorphosis.

Notch Moth Caterpillar (Tmetolophota steropastis)

The harakeke notch moth caterpillar also feed nocturnally on young flax leaves, leaving triangular shaped holes called 'notches' along the edges. To do this, it has jaws outside of the mouth (structural adaptation) that move sideways, biting chunks off the leaf edges.

Notch moth caterpillars are brown-yellow (not pictured) and also metamorphose into an adult moth (pictured).

Looking at the picture of a caterpillar head above, what do you think the jaws of each caterpillar would be like?

Are the two species of harakeke moth caterpillars competing for the same food?

We carried out an investigation to answer this question. We found a harakeke bush with lots of windows and notches in the leaf, and took the following measurements for 5 notches and 5 windows:

Distance from the midrib to the:

  • start of the notch

  • edge of the leaf

  • start of the window

  • end of the window

Analyse this graph of our results (left). Think about these questions:

  • Do the bars of the graph overlap?

  • Do you think the caterpillars are competing for the same food? Why?

  • What do you think would eventually happen to the caterpillars if they ate exactly the same part of the leaf?

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