Biological Classification
Classification groups organisms by shared features, similarities, and differences so living things can be identified and studied systematically.
Lesson 1:
Biodiversity
and
Classification
Learn how biologists classify living organisms, use observable and molecular features, apply dichotomous keys, and connect biodiversity terms to exam-style questions.
Section
A
Unit
1
Quiz
12 marks
Classifying Life on Earth
Use the video first, then move into the summary, flashcards, and quiz.
Study Guide Summary
Core ideas to know before attempting the quiz.
Evidence Used
Biologists use observable external and internal features, and modern classification also uses molecular evidence such as proteins and DNA.
Dichotomous Keys
A dichotomous key identifies organisms through paired choices, with only two options at each step until the organism is named.
Species
A species is a group of organisms that can breed together to produce fertile offspring.
Ecology Terms
Know habitat, population, community, environment, niche, and ecosystem. These terms are common in CSEC exam questions.
Sampling Practice
Be ready to calculate mean density and population estimates using mark-release-recapture data.
Lesson Flashcards
Open each card, check your answer, then close it and test yourself again.
Classification Principles
Biological classification is the process of grouping organisms based on shared features and physical similarities and differences.
It helps biologists organize, identify, and study living things in a systematic way.
It guides identification through a series of paired choices, with only two options at each step.
DNA and protein evidence can show relationships more precisely than visible features alone.
Major Groups and Energy Flow
Plants, animals, and microorganisms. Microorganisms include groups such as bacteria and fungi.
They feed on dead and decaying matter by secreting enzymes, helping recycle carbon and nitrogen.
Green plants produce food by photosynthesis using energy from sunlight.
Animals cannot make their own food and must feed on plants or other animals for energy.
Species and Ecology Terms
A species is a group of organisms that can breed together to produce fertile offspring.
A two-part scientific naming system. The first part is the genus and the second part identifies the species.
A habitat is where an organism lives. A population is all members of one species in a habitat. A community is all organisms living in a particular place.
A niche is the role of a species in an ecosystem. An ecosystem includes a community plus all biotic and abiotic factors that affect it.
Exam Applications
The mangrove tree is the producer. The moth caterpillar is the primary consumer because it feeds on mangrove leaves.
Estimated population = (number marked first x total number in second sample) / number of marked individuals in second sample.
Estimated population = (33 x 16) / 7 = 528 / 7 = about 75 beetles.
Biological control is the use of predators or parasites to reduce pest species without relying on chemical pesticides.
Self-Assessment Quiz
Choose one answer for each question. Submit when ready to see your score.