Fiche de révision : Fundamentals of Living Organisms

📋 Course Outline

1. Characteristics and classification of living organisms
2. Cell structure, organelles, and biological molecules
3. Movement of substances, nutrition, and respiration in organisms
4. Gas exchange, transport systems, and excretion in plants and animals
5. Coordination, response, and homeostasis in living organisms
6. Reproduction, inheritance, and genetic variation
7. Ecology: populations, communities, ecosystems, and environmental factors
8. Use of biological resources: food production, selective breeding, and genetic modification

📖 1. Characteristics and classification of living organisms

🔑 Key Concepts & Definitions

• Excretion : The removal of metabolic waste products from the organism.
• Pathogen : A microorganism that causes disease, including fungi, bacteria, protoctists, and viruses.
• Living Organisms : The Nature and Variety of Living Organisms 2.

📝 Essential Points

• All living organisms carry out nutrition, respiration, excretion, sensitivity, movement, control (homeostasis), reproduction, and growth and development.
• Plants are multicellular eukaryotes with chloroplasts, cell walls made of cellulose, and store carbohydrates as starch or sucrose.
• Animals are multicellular eukaryotes without chloroplasts or cell walls, have nervous coordination, usually move, and store carbohydrates as glycogen.
• Viruses are not living organisms, are smaller than bacteria, parasitic, reproduce only inside living cells, have no cellular structure, and contain either DNA or RNA.

💡 Key Takeaway

All living organisms carry out nutrition, respiration, excretion, sensitivity, movement, control (homeostasis), reproduction, and growth and development.

📖 2. Cell structure, organelles, and biological molecules

🔑 Key Concepts & Definitions

• Biology : a branch of science that studies living organisms and their vital processes.

• Organelle levels of organisation : a sequence in biological structure where structures progress from small, specialized components to larger, integrated systems, including organelles, cells, tissues, organs, and organ systems.

• Plant cells : eukaryotic cells characterized by the presence of cell walls, chloroplasts, and large permanent vacuoles, which are absent in animal cells.

• Animal cells : eukaryotic cells that lack cell walls, chloroplasts, and large vacuoles, differentiating them from plant cells.

• Enzymes : biological catalysts that accelerate metabolic reactions by lowering activation energy; they possess specific active sites that bind to substrates and are affected by temperature and pH.

• Biological molecules : organic compounds essential for life, including carbohydrates, lipids, and proteins, each composed of specific elements and identifiable through particular food tests.

📝 Essential Points

• The levels of organisation in cells start with organelles, which are specialized structures within cells. These organelles combine to form the cell itself. Cells then group into tissues, which perform specific functions. Tissues combine to form organs, which are part of larger organ systems that coordinate complex biological activities.

• Plant cells contain unique features such as cell walls, which provide structural support; chloroplasts, where photosynthesis occurs; and large permanent vacuoles that store water and maintain cell turgidity. In contrast, animal cells do not have these features, reflecting differences in structure and function.

• Enzymes act as biological catalysts with specific active sites that facilitate reactions. Their activity can be influenced by environmental factors like temperature and pH, which can alter their shape and effectiveness, thus impacting metabolic processes.

• Biological molecules include carbohydrates, lipids, and proteins. Carbohydrates are identified by tests such as Benedict’s (for reducing sugars) and iodine (for starch). Lipids can be detected through ethanol emulsion tests, while proteins are identified using the Biuret test. Each molecule is composed of particular elements, such as carbon, hydrogen, oxygen, and nitrogen.

💡 Key Takeaway

Mastering cell components and biological molecules reveals the biochemical foundation of life functions.

📖 3. Movement of substances, nutrition, and respiration in organisms

🔑 Key Concepts & Definitions

• Active Transport : A process that moves substances from an area of low concentration to an area of high concentration using energy.
• Amino acids : Organic compounds that are the building blocks of proteins.
• Fatty acids + glycerol : Components that combine to form lipids such as fats and oils.

📝 Essential Points

• Diffusion is the net movement of particles from high to low concentration without energy.
• Osmosis involves water moving through a partially permeable membrane from high to low water potential.
• Aerobic respiration converts glucose and oxygen into carbon dioxide and water, releasing energy stored in ATP.

💡 Key Takeaway

Grasping how substances move across membranes and how energy is released through respiration is essential for understanding how organisms survive and function.

📖 4. Gas exchange, transport systems, and excretion in plants and animals

🔑 Key Concepts & Definitions

• Transport System : A biological system that facilitates the movement of substances within an organism.
• Carbon dioxide : A waste product of respiration that is transported in the blood to the lungs for exhalation.
• Large surface area ● thin walls : A feature of alveoli that facilitates efficient gas exchange.

📝 Essential Points

• Phloem transports sucrose and amino acids from leaves to other parts of the plant.
• Red blood cells have biconcave shape, no nucleus, and contain haemoglobin to transport oxygen.

💡 Key Takeaway

Comprehending specialized structures and transport systems explains how organisms efficiently exchange gases and distribute substances.

📖 5. Coordination, response, and homeostasis in living organisms

🔑 Key Concepts & Definitions

• Homeostasis : Biological regulation of internal conditions to maintain stability, such as body temperature and water content.
• Nervous System : Network including the central nervous system and nerves that transmit electrical impulses linking sense organs to the brain and spinal cord.
• Blood cells : Cells in blood including red blood cells, white blood cells, and platelets, each with specific functions.

📝 Essential Points

• Homeostasis maintains stable internal conditions like body temperature and water content.
• Hormones are chemical messengers regulating processes such as blood glucose and menstrual cycle.

💡 Key Takeaway

Understanding coordination and regulation mechanisms reveals how organisms maintain internal stability and respond to stimuli.

📖 6. Reproduction, inheritance, and genetic variation

🔑 Key Concepts & Definitions

• Sexual reproduction : biological process involving two parents that produce offspring through the fusion of gametes, resulting in genetic variation among the offspring.

• Asexual reproduction : biological process where a single parent produces genetically identical offspring without the involvement of gametes.

• Gene : a segment of DNA that encodes the instructions for making proteins and is located on chromosomes within the nucleus.

• Allele : different versions of a gene that determine specific inherited traits, contributing to genetic diversity.

📝 Essential Points

• Sexual reproduction requires two parents and involves the fusion of gametes, which leads to offspring with a mix of genetic material from both parents, thereby producing genetic variation.

• Asexual reproduction involves only one parent, which produces offspring that are genetic clones of the parent, without the involvement of gametes.

• Genes are specific sections of DNA that carry the instructions for protein synthesis and are situated on chromosomes inside the nucleus.

• Alleles are alternative forms of a gene; their variation influences inherited traits and contributes to diversity within a species.

💡 Key Takeaway

Understanding reproductive modes and genetic principles is essential for grasping how inheritance occurs and how genetic diversity is maintained in populations.

📖 7. Ecology: populations, communities, ecosystems, and environmental factors

🔑 Key Concepts & Definitions

• Population : a group of individuals belonging to the same species within a specific area, characterized by their shared genetic makeup and interactions.

• Community : all the different organisms, encompassing multiple species, living and interacting within a defined area.

• Ecosystem : the biological community combined with its physical environment, including both living organisms and non-living environmental factors that influence them.

• Abiotic Factor : non-living environmental elements such as light, temperature, water, soil pH, mineral content, oxygen, and carbon dioxide that impact the survival and functioning of organisms.

📝 Essential Points

• A population consists of one species in a particular area, while a community includes all organisms present in that area, regardless of species. An ecosystem extends this concept by integrating the community with its environment, which includes abiotic factors like light, temperature, water, soil pH, mineral content, oxygen, and carbon dioxide. Food chains illustrate single feeding pathways, whereas food webs depict interconnected chains, showing the complex feeding relationships within a community. Energy transfer between trophic levels is approximately 10%, with the remaining energy lost as heat, movement, or waste, emphasizing the inefficiency of energy flow in ecosystems.

💡 Key Takeaway

Understanding ecological levels and environmental influences is essential for grasping how organisms interact and how energy moves through ecosystems.

📖 8. Use of biological resources: food production, selective breeding, and genetic modification

🔑 Key Concepts & Definitions

• Food production : The process of producing food for human consumption, including farming and related activities.
• Selective breeding : A technique that develops plants and animals with desired traits by choosing parents with specific characteristics.
• Genetic Modification : The process of transferring genes between species using restriction enzymes, ligase, and vectors to produce desired traits.

📝 Essential Points

• Selective breeding develops plants and animals with traits like disease resistance and higher yields.
• Fermenters provide controlled conditions for microorganisms to produce products such as insulin and yoghurt.
• Pesticides are effective for pest control but can harm beneficial organisms and cause pollution.

💡 Key Takeaway

Using biological technologies and breeding strategies enhances food production and resource management.

📊 Synthesis Tables

Characteristics of Living Organisms

Cell Structure and Biological Molecules

⚠️ Common Pitfalls & Confusions

1. Confusing viruses with living organisms due to their ability to reproduce.
2. Assuming all multicellular organisms are plants or animals, ignoring other kingdoms.
3. Mixing up features of plant and animal cells, such as chloroplasts and cell walls.
4. Overlooking the role of enzymes as biological catalysts.
5. Misunderstanding the difference between genetic inheritance and environmental influence.
6. Confusing the direction of energy flow in food chains and webs.
7. Assuming all microorganisms are harmful or pathogenic.

✅ Exam Checklist

1. Identify features that distinguish plant and animal cells.
2. Describe the role of enzymes in metabolic reactions.
3. Explain how gases are exchanged in alveoli.
4. Describe the process of photosynthesis in chloroplasts.
5. Compare sexual and asexual reproduction.
6. Explain how homeostasis maintains internal stability.
7. Identify the components of a biological transport system.
8. Describe the process of genetic modification.
9. Explain the importance of biodiversity in ecosystems.
10. Discuss the use of selective breeding in agriculture.