Ecology O2 Nutrients CO2 Ecology is the study of the relationships between organisms and their physical and biotic environment: Relationships involve interactions with the physical world as well as interrelationships with other species and individuals of the same species.

Biological Complexity Living organisms can be studied at different levels of complexity. From least to most complex, these levels are (in an ecological context): Individual Population Community Ecosystem Biome Biosphere Biosphere Biome Ecosystem Community Population Individual

The Biosphere The biosphere is the region within which all living things are found on Earth. It is the narrow belt around the Earth extending from the bottom of the oceans to the upper atmosphere. Image: NASA

Exploring the Biosphere Life exists in all places, from blind white crabs in lightless environments... Our knowledge of what constitutes the biosphere continues to develop as scientists continue their exploration of the Earth. The biosphere extends into the Earth’s crust, below the oceans and deep into rock fissures; it extends well into the Earth’s upper atmosphere. to tube worms in the crushing ocean depths.

Lichens are found on rocks, trees, and bare ground. Habitat An organism’s habitat is the physical place or environment in which it lives. Organisms show a preference for a particular habitat type, but some are more specific in their requirements than others. Most frogs, like this leopard frog, live in or near fresh water, but a few can survive in arid habitats. Lichens are found on rocks, trees, and bare ground.

Habitat Range An organism’s habitat is not always of a single type. Some organisms occupy a range of habitats. There are various reasons why: Highly adaptable in habitat requirements. Different, but equivalent, resources available in different habitats. Reduced competition for resources in sub-optimal habitats. Habitat extremes may influence growth form, especially in plants.

Habitat Preference Organisms may select particular areas within their general habitat, even in apparently homogeneous environments, such as water. This is termed habitat preference. Example: Aquatic organisms may show a preference for a particular substrate type, water depth or velocity, water clarity, or degree of vegetation cover or habitat disturbance. Knowledge of habitat preference can be used to protect species in their environment. Damselfly nymph Rainbow trout

Resources in a Habitat The habitat provides organisms with the following resources: Food and water sources Mating sites Nesting sites Predator avoidance Shelter from climatic extremes However, the organism may or may not have the adaptations to exploit all the available resources fully.

Adaptations An adaptation (or adaptive feature) is an inherited feature of an organism that enables it to survive and reproduce in its habitat. Adaptations are the end result of the evolutionary changes that a species has gone through over time. Adaptations may be: behavioral physiological structural (morphological) Osprey: a diurnal bird of prey Spotted owl: a nocturnal bird of prey

Exploiting a Habitat Organisms have adaptations to exploit, to varying extents, the resources in their habitat. Where resource competition is intense, adaptations enable effective niche specialization and partitioning of resources. In the African savanna, grazing and browsing animals exploit different food resources within the same area or even within the same type of vegetation.