1. Characteristics & classification of living organisms (Cambridge IGCSE Biology 0610 2023,24 & 25)

Summary

This IGCSE study video explores the characteristics and classification of living organisms. It covers the seven vital characteristics organisms must possess, using the 'Mrs Green' mnemonic to remember them. The video introduces the binomial nomenclature for species naming and explains the use of dichotomous keys for identification. It delves into the five kingdoms of life, detailing the features of each and further subdividing them into classes and groups. The video also clarifies that viruses, lacking cellular structure, are not classified within these systems.

Takeaways

• 🧬 Biology is the study of living organisms, which exhibit seven key characteristics: Movement (M), Respiration (R), Sensitivity (S), Growth (G), Reproduction (R), Excretion (E), and Nutrition (N).
• 🌿 Organisms are classified into species, which are groups that can interbreed to produce fertile offspring, and further organized into groups based on shared features.
• 🔬 The binomial system is used to name species scientifically, consisting of a genus and species name, with the genus capitalized and species in lowercase.
• 🔑 Dichotomous keys are tools for identifying organisms by answering a series of binary questions based on their characteristics.
• 📚 Classification systems group organisms to reflect evolutionary relationships, moving from broad categories like kingdoms to more specific groups like species.
• 🐾 The five major kingdoms of life are Animalia, Plantae, Fungi, Protista, and Prokaryotes, each with distinct cellular and nutritional characteristics.
• 🦴 Vertebrates are a subgroup of animals with a backbone, divided into mammals, birds, reptiles, amphibians, and fish based on specific anatomical and physiological traits.
• 🦋 Invertebrates lack a backbone and include arthropods, which are further classified into myriapods, insects, arachnids, and crustaceans based on the number of legs and other features.
• 🌱 The Plantae kingdom includes ferns, which reproduce via spores, and flowering plants, which are divided into monocotyledons and dicotyledons based on seed and leaf structure.
• 🦠 Viruses are not considered living organisms as they cannot carry out life processes independently and require a host cell to replicate.

Q & A

What are the seven characteristics that define living organisms?

The seven characteristics that define living organisms are movement (M), respiration (R), sensitivity (S), growth (G), reproduction (R), excretion (E), and nutrition (N).

What does the term 'sensitivity' refer to in living organisms?

Sensitivity refers to the ability of an organism to detect and respond to changes in its internal or external environment.

How does the binomial system of naming species work?

The binomial system of naming species is an internationally agreed system where the scientific name of an organism consists of two parts: the genus (capitalized) and the species (lowercase), indicating the organism's classification within a group of related species.

What is a dichotomous key and how is it used?

A dichotomous key is a tool used to identify organisms based on a series of questions about their features. It branches into two choices at each step, leading to more specific descriptions until the organism's name is identified.

What is the purpose of classification systems in biology?

The purpose of classification systems in biology is to organize the vast diversity of life into groups based on shared characteristics, making it easier to study and understand the evolutionary relationships between different species.

How are organisms classified into the five kingdoms?

Organisms are classified into five kingdoms based on their cellular structure and mode of nutrition: animals, plants, fungi, protists, and prokaryotes.

What are the main features that distinguish animals from other kingdoms?

Animals are multicellular, have cells with a nucleus but no cell walls or chloroplasts, and obtain nutrition by consuming other living things.

What are the characteristics of vertebrates within the animal kingdom?

Vertebrates are animals with a backbone and include mammals, birds, reptiles, amphibians, and fish. They are characterized by having a spinal column and complex organ systems.

How do monocotyledons and dicotyledons differ in terms of leaf structure?

Monocotyledons have parallel leaf veins, while dicotyledons have broader leaves with branching veins.

Why are viruses not considered to be part of any classification system?

Viruses are not considered part of any classification system because they do not possess cellular structures and cannot carry out life processes independently; they require a host cell to replicate.