4.1 Species, Communities and Ecosystems

What does Ecology studies?

Studies how **living things interact** with each other and the environment

Biotic factors

**Living conditions** that affect **organism survival.**

* Include sources of competition (intra-specific / inter-specific) and predators

Abiotic factors

**Non-living** conditions that affect **organism survival.**

* Temperature, availability of light or rain, levels of pollution, etc.

Species

Groups of organisms that **interbreed** to produce **fertile, viable offspring.**

* **Hybrid** species are the **infertile** offspring of two distinct species (e.g. mules)

Populations

Groups of organisms of the **same species** living in the **same area** at the **same time**

* e.g. populations of squid and crabs within an aquatic ecosystem.

Community

Groups of populations of **different** species that **live within a given area and** __**interact.**__

* The environment in which a species lives (its normal location) is called a **habitat.**

Ecology Terms: **Ecosystem**

**All** of the **communities** within a given **environmental region.**

* It is composed of both __biotic__ factors (communities) and __abiotic__ factors (habitat).

Summary of Ecology Terms

Nutrition

Uptake of both **energy** and materials from **environmental sources**.

* It occurs via an **autotrophic** (self source) or **heterotrophic** (other source) method.

Some organisms may use **both** forms of nutrition according to need (mixotrophs)

Autotrophs

**Synthesize** organic molecules (food) from simple inorganic substances.

* As they are making their **own organic compounds**, they are called ==__**producers**__==.

Inorganic nutrients needed for this process are obtained from **air, water and soil**.

* Most will derive the required energy from **sunlight** ***(photosynthesis)****.*
* Some from inorganic redox reactions ***(chemosynthesis).***

Heterotrophs

Obtain organic molecules from other organisms via acts of **feeding**.

* This organic material is originally synthesized by autotrophs (*i.e. the producers*)

How are heterotrophs classified?

According to their feeding pattern.

* **Consumers**
* **Detritivores**
* **Saprotrophs**
* **Scavengers**

Heterotrophs: Consumers

Ingest **organic matter from living** (or recently killed) organisms.

* Herbivores = plant matter.
* Carnivores = animal matter.
* Omnivores = both

Heterotrophs: Detritivores

Obtain nutrients from **non-living organic material** (i.e. detritus, which is a waste of any kind).

* Detritus may include **fecal material** or decaying leaf litter in the soil (humus).

Heterotrophs: Saprotrophs

Obtain organic nutrients from **dead organisms** by external digestion (they are *decomposers*)

Heterotrophs: Scavengers

Feed on decaying biomass (i.e. carrion)

Closed Ecosystems

Two conditions for the **sustainability** of an ecosystem:

* **Energy influx** – sunlight provides **initial energy** **source** for most communities.
* **Nutrient cycling** – **saprotrophic decomposers** recycle nutrients in ecosystems.

Mesocosm

**Enclosed** environments that allow a small part of a natural environment to be **observed** under ^^**controlled conditions**^^ (e.g. sealed terrariums)

Ecological Measurements

Biotic conditions (e.g. species distribution) in __open ecosystems__ can be measured

* **Quadrats**: **rectangular** frames of known dimensions (used for *sampling*).
* **Transects**: **straight** lines along a defined abiotic gradient (*elevation*)