IGCSE Bio Topic 1

What does the acronym MRS GREN stand for in the context of characteristics of living organisms?

M: Movement, R: Respiration, S: Sensitivity, G: Growth, R: Reproduction, E: Excretion, N: Nutrition.

What is the purpose of classifying living organisms?

To simplify study and reflect evolutionary relationships.

How is a species defined?

Organisms that can interbreed to produce fertile offspring.

What is the Binomial System of naming organisms?

A scientific naming system comprising two parts: Genus (capitalized) and species (lowercase), always italicized.

What are dichotomous keys used for?

To identify organisms via a branching series of questions based on physical features.

What are the five kingdoms of living organisms?

Animals, Plants, Fungi, Protoctists, Prokaryotes.

What are the characteristics of vertebrates?

Animals with backbones, which are divided into five groups: Mammals, Birds, Reptiles, Amphibians, and Fish.

What distinguishes monocotyledons from dicotyledons?

Monocotyledons have parallel leaf veins and multiples of 3 petals; dicotyledons have branched leaf veins and multiples of 4 or 5 petals.

Why are viruses not classified in the kingdoms of living organisms?

Because they are considered non-living and require a host cell to reproduce.

Explain the significance of DNA sequencing in classification.

DNA base sequences reveal evolutionary relationships, with similar DNA indicating a more recent common ancestor.