BlogBiologyThe Essential List of QCAA Biology Terms You Need to Know for Unit 3

The Essential List of QCAA Biology Terms You Need to Know for Unit 3

Ladybug on a green leaf - Biology Terms Featured Image

Finding it hard to remember all the key terms you’ve studied in Unit 3 for QCAA Biology?

Don’t worry! We’ve got you covered with our list of QCAA Biology terms — you’ll also be able to download our list to have on hand.

What are you waiting for? Let’s get into it!

QCAA Biology Terms

A | BC | D | E | F | G | H | I | J | KL | M | N | O | P | QR | S | T | U | V | W | X | Y | Z


Physical or chemical components of the environment that are non-living and impact living organisms, as well as the functioning of the ecosystem.


A measure of the variation of life on Earth — including genetic variation or the number of species in an area.


Organic material in the environment. 


Components of the environment that are living.

Carrying Capacity

The size of the population that can be supported indefinitely on the available resources and services of that ecosystem. 

QCE Biology Terms - Carrying Capacity

Image sourced from


A group of organisms that consist of a common ancestor and all its lineal descendants. 

QCE Biology Terms - Clade

Image sourced from Understanding Evolution


An approach to classification that categorises organisms based on hypotheses about group/individual relatedness and common ancestry. Typically, it is based on shared characteristics.


An evolutionary tree that indicates relationships between individuals – based on shared phenotypes. 

QCE Biology Terms - Cladogram

Image sourced from Research Gate


Arrange, distribute or order is classes or categories according to shared qualities or characteristics. 

Climax Community

A stable community of organisms in the final stage of succession.


The rivalry between individuals or groups of organisms for resources such as food, shelter, sunlight, and mates. It is an example of a symbiotic relationship.

Competitive Exclusion Principle

Two species cannot occupy the same niche and stably coexist — due to requiring the same resources.


An abnormal condition (impacting structure or function) that negatively affects the organism.

Ecological Niche

The role and space that an organism fills in an ecosystem, including all its interactions with the biotic and abiotic factors of its environment.

Ecological Succession

The steady and gradual developmental process of ecosystems from bare ground to climax community. 

Ecological Succession

Image sourced from Living Nature


Areas containing ecosystems of similar characteristics. Each ecoregion has geographically distinct collections of communities. 


An area where organisms interact with each other and the physical environment surrounding them, and different biotic and abiotic components are linked through nutrient cycles and energy transfers.


Moving away from your place of residence.

Remember to incorporate these definitions in your study notes by learning how to take effective study notes for science!


An area occupied by organisms. It includes the elements surrounding the organisms as well.


An array of resources, abiotic and biotic factors, present in a given area, that aid the survival of particular species.


The movement into a new location. 

Interspecific Hybrid

The offspring of parents from two different species.

Keystone Species

A plant or animal that plays a unique and crucial role in the way an ecosystem functions.

Lincoln Index

A means of estimating the population size of a given animal species. It works by capturing, marking, releasing and then recapturing individuals from the species of interest.

Linnaean System

A classification system that places organisms into groups depending upon their physical characteristics. 

Linnaean system

Image sourced from Woo! Jr.


A subsection of a habitat that hosts unique conditions — differing from the surrounding, larger habitat. Microhabitats may be home to specific species that cannot live in the larger habitat. 

Nitrogen Fixation

The process in which nitrogen in the air is liberated — converting it into ammonia or another nitrogenous compound (usually to be used by plants).

Percentage Cover

A measure of the influence that a particular plant species has on the ecosystem and how much space it is taking up.


The process by which photosynthetic autotrophs use sunlight, water, and carbon dioxide to generate oxygen and glucose. 


Image sourced from Ducksters

Pioneer Species

The first species to colonise a previously barren environment. Typically, they are hardy species capable of withstanding extreme conditions, able to perform photosynthesis, germinate quickly and fixate nitrogen.


A biological interaction in which an organism kills and eats another organism.

Primary Succession

The first time an area is being colonised by plants and animals. In this form of succession, the area is void of vegetation and usually lacking soil.


Traditionally a square frame used to study the distribution of organisms within the marked area. 

QCE Biology Terms - Quadrat

Image sourced from Practical Biology

Relative Species Abundance

A measure of the composition of organisms in an ecosystem/area that is made up by a particular species.

Secondary Succession

The second time an area is being colonised. This form of succession occurs after some major disturbance removes the primary species present in an area.


An intermediate stage on the way to a climax community in the process of ecological succession.

Simpson’s Diversity Index

A measure of biodiversity that accounts for not only the number of species present in a given area, but also the relative abundance of each of those species.


Relating to space.


Two organisms that are able to reproduce naturally to produce viable and fertile offspring.

Species Richness

The number of species in a given area.

Stratified Sampling

A type of sampling in which a sample is taken of each strata of the population.


The relationship or interaction between organisms from two different species.


Relating to time.


A line set across a given area, from which the number of organisms in each species along the transect is counted. 

QCE Biology Terms - Transect

Image sourced from Research Gate

Trophic Level

The position that an organism has in the food chain. 

Trophic Level

Image sourced from CK-12

On the hunt for other QCAA Biology resources?

You can never have enough practice questions, so lucky for you, we’ve got many that you can work through. Check them out below:

We’ve collated all the key resources that you’ll need to completeTerm 1 of Year 12We’ve also got everything you need to know about getting ready for your QCE IA1.

We’ve also got some handy guides for tackling your QCAA Biology assessments that you should check out:

Also studying Physics Unit 3? Check out our guide on Unit 3: Gravity and Electromagnetism

Are you looking for some extra help with understanding QCAA Biology terms?

We have an incredible team of QLD Biology tutors and mentors!

About to begin Year 12? Take our Year 12 Readiness quiz to see how you compare to the rest!

We can help you master the QCAA Biology syllabus and ace your upcoming Biology assessments with personalised lessons conducted one-on-one in your home or online!

We’ve supported over 8,000 students over the last 11 years, and on average our students score mark improvements of over 20%!

To find out more and get started with an inspirational QLD tutor and mentor, get in touch today or give us a ring on 1300 267 888!

Katelyn Smith was a pioneer in the Queensland ATAR system. After graduating in 2020 with an ATAR of 98.40, she now studies a Bachelor of Advanced Science (Honours) at The University of Queensland — majoring in Physics. Through her studies, she hopes to develop a greater appreciation for how the wonders of the universe work. When she isn’t slaving away behind her unnecessarily large textbooks, she enjoys catching up with friends, scrolling mindlessly through TikTok, and sleeping.

45,861 students have a head start...

Get exclusive study content & advice from our team of experts delivered weekly to your inbox!

AOS Website Asset 2

Looking for Biology Support?

Discover how we can help you!

AOS Website Asset 1