🌐 The Seven Essential Requirements
All living organisms require these seven things to survive:
- Water
- Food/nutrients
- Oxygen (for most organisms)
- Suitable temperature
- Space
- Removal of waste
- Ability to reproduce
Characteristics of Living Organisms » Requirements of Living Organisms
What you'll learn this session
Study time: 30 minutes
- The seven essential requirements for all living organisms
- How organisms obtain and use water, food and oxygen
- The importance of temperature regulation in living things
- How organisms remove waste products
- Why living things need space to grow and reproduce
Requirements for Living Organisms
All living organisms, from the tiniest bacteria to the largest blue whale, need certain things to stay alive. These requirements are universal - every living thing needs them, though they might get them in different ways.
Key Definitions:
- Requirements: The essential things that all living organisms need to survive and function properly.
- Metabolism: All the chemical processes that occur within a living organism to maintain life.
🚀 Why These Matter
Without these requirements, organisms cannot:
- Grow and develop
- Maintain their internal environment
- Respond to their surroundings
- Reproduce and pass on their genes
- Carry out essential life processes
Water: The Universal Solvent
Water is arguably the most important requirement for life. Around 60-70% of your body is water!
Why Water is Essential
Water plays many crucial roles in living organisms:
💧 Transport
Water carries dissolved substances around organisms. In humans, blood plasma is mostly water and transports nutrients, hormones and waste products.
🧪 Chemical Reactions
Most metabolic reactions happen in water solutions. Digestion, respiration and photosynthesis all require water.
🌡 Temperature Control
Water has a high specific heat capacity, which helps regulate body temperature. Sweating in humans and transpiration in plants cool organisms down.
Case Study Focus: Desert Adaptations
Camels can survive for weeks without drinking by conserving water. They can tolerate losing up to 25% of their body weight in water and their humps store fat (not water) for energy. Their kidneys and intestines are extremely efficient at retaining water and they produce concentrated urine to minimise water loss.
Food and Nutrients
All organisms need energy and materials to grow, repair damage and carry out life processes.
How Organisms Get Food
Living things obtain food in different ways:
🌱 Autotrophs
These organisms make their own food. Plants, algae and some bacteria use photosynthesis to convert light energy into chemical energy (glucose). The equation for photosynthesis is:
Carbon dioxide + Water → Glucose + Oxygen
This happens in the presence of light and chlorophyll.
🐶 Heterotrophs
These organisms cannot make their own food and must consume other organisms. Animals, fungi and many bacteria are heterotrophs. Humans need to eat a balanced diet containing:
- Carbohydrates for energy
- Proteins for growth and repair
- Fats for energy storage and insulation
- Vitamins and minerals for various metabolic functions
Oxygen
Most living organisms need oxygen to release energy from food through respiration.
Aerobic Respiration
This is the process that breaks down glucose using oxygen to release energy:
Glucose + Oxygen → Carbon dioxide + Water + Energy
The energy released is used for all life processes, from muscle contraction to cell division.
🛫 Getting Oxygen
Different organisms have different ways of obtaining oxygen:
- Humans and mammals: Breathe through lungs
- Fish: Extract oxygen from water using gills
- Insects: Take in oxygen through a network of tubes called tracheae
- Plants: Absorb oxygen through small pores called stomata
🦠 Anaerobic Organisms
Some organisms can live without oxygen. These include certain bacteria that use anaerobic respiration or fermentation to release energy. Some parasitic worms can also survive in oxygen-poor environments inside their hosts.
Suitable Temperature
Temperature affects the rate of chemical reactions in living organisms. Each species has an optimal temperature range where its enzymes work best.
Temperature Regulation
Organisms can be classified based on how they regulate their body temperature:
🐅 Endotherms
These animals (like mammals and birds) can maintain a constant internal body temperature regardless of their environment. They generate heat through metabolism and have adaptations like fur, feathers and sweat glands to regulate temperature.
🐊 Ectotherms
These animals (like reptiles, amphibians and fish) rely on external sources of heat. Their body temperature changes with their environment. They use behavioural adaptations like basking in the sun or seeking shade to regulate their temperature.
Case Study Focus: Extreme Environments
Some organisms can survive in extreme temperatures. Thermophilic bacteria live in hot springs at temperatures up to 80°C. At the other extreme, Antarctic fish produce antifreeze proteins that prevent their blood from freezing in sub-zero waters. These adaptations show how different organisms have evolved to meet their temperature requirements in various environments.
Waste Removal
All living organisms produce waste that must be removed to prevent it from becoming toxic.
Types of Waste Products
Different metabolic processes produce different waste products:
- Carbon dioxide: Produced during respiration and removed through lungs, gills, or stomata
- Nitrogenous waste: From protein breakdown, excreted as urea, uric acid, or ammonia
- Water: Can be a waste product of respiration or excess water intake
- Undigested food: Removed as faeces
💪 Human Excretion
Humans remove waste through several organs:
- Lungs: Remove carbon dioxide
- Kidneys: Filter blood and produce urine
- Skin: Removes water and salts through sweat
- Liver: Processes toxins for removal
🌱 Plant Waste
Plants have different waste removal methods:
- Oxygen (from photosynthesis) released through stomata
- Carbon dioxide (from respiration) released through stomata
- Some waste stored in leaves that fall off
- Some waste stored in vacuoles within cells
🐟 Aquatic Animals
Fish and aquatic invertebrates have special adaptations:
- Ammonia excreted directly into water through gills
- Some have nephridia or other specialized excretory structures
- Marine fish must conserve water while removing salt
Space and Reproduction
All organisms need space to grow, find resources and reproduce. Overcrowding can lead to competition for limited resources like food, water and shelter.
Space Requirements
Different organisms need different amounts of space:
- Plants need space for their roots to spread and leaves to access sunlight
- Animals need territories for hunting, mating and raising young
- Even microorganisms need space to avoid overcrowding and resource depletion
Reproduction
Reproduction ensures the survival of species. All living organisms have adaptations that allow them to reproduce successfully:
- Plants may produce seeds that can be dispersed to new areas
- Animals may migrate to find mates or suitable breeding grounds
- Many organisms time their reproduction to coincide with favourable conditions
Case Study Focus: Population Dynamics
When a population exceeds the carrying capacity of its environment, resources become scarce. This can lead to increased competition, disease and even population crashes. For example, reindeer introduced to St. Paul Island in Alaska in 1911 had no natural predators. Their population grew from 4 to 2,000 in 30 years, destroying their food source. The population then crashed to just 8 animals by 1950. This demonstrates how space and resources limit population growth.
Summary: The Interconnected Requirements
All seven requirements for life are interconnected. For example:
- Water is needed to transport nutrients from food
- Oxygen is used to release energy from food
- Temperature affects the rate of all metabolic processes
- Waste removal depends on water and appropriate space
- Reproduction requires energy from food and suitable environmental conditions
Understanding these requirements helps us appreciate how different organisms are adapted to their environments and how changes in these environments can affect their survival.
Access the full course and all the resources like custom timetables and progress tracking.
Join Today