IB HL Biology 4.1 Species, Communities, and Ecosystems

Species

A group of organisms that can interbreed to produce viable, fertile offspring

* Limitations: Can’t refer to asexually reproductive groups → use it anyway

Population

A group of organisms of the same species living in the same area at the same time

Habitat

Type of environment in which an organism or group naturally lives

Community

A group of populations living and interacting in an area

Ecosystem

A community and its abiotic environment

Abiotic

Non-living

Autotroph

Synthesises its organic molecules from simple inorganic substances

Heterotroph

Obtains organic molecules from other organisms

Nutrient

Chemical substances needed by organisms to survive

Consumer

Heterotrophs that feed on living/recently killed organisms via ingestion

Detritivore

Heterotroph that feeds on detritus(non-living organic matter) by internal digestion

Saprotroph

Heterotroph that lives in non-living organic matter and secretes digestive enzymes that absorb nutrients(external digestion)

Nutrient Cycling

chemical elements can be recycled but energy cannot

* water and air penetrate soil → plant/animal matter breaks down into soil → decomposers break down organic matter + rocky subsoil breaks down providing nutrients → soil stores nutrients which plants absorb → nutrients used to grow

Ecosystem Sustainability

Able to provide for the needs of organisms without intervention over a long period of time

Energy Availability + Nutrient Availability + Recycling of Wastes

Mesocosm

Mesocosm: Experimental tool that brings a small part of the natural environment under controlled conditions