ZOOL LECTURE PRELIMS.pdf

PRELIMINARY 24-25 Part 1: Biological Principles and the Science of Zoology Zoology A branch of biology that focuses on the study of animals, from their physical structure to their behavior and interactions within ecosystems. Zoologists seek to understand the...

PRELIMINARY 24-25 Part 1: Biological Principles and the Science of Zoology Zoology A branch of biology that focuses on the study of animals, from their physical structure to their behavior and interactions within ecosystems. Zoologists seek to understand the ○ diversity of animal life, ○ how animals evolve, and ○ the various biological processes that sustain them, such as metabolism, growth, reproduction, and development. General Properties of Living System Living organisms, including animals, share several properties that distinguish them from non-living matter: ❖ Chemical Uniqueness One of the defining features of life is its unique chemical composition. All living organisms are built from large, complex molecules known as macromolecules, which play essential roles in biological functions. PRELIMINARY 24-25 These macromolecules include: Proteins: Made up of amino acids linked in chains, proteins perform various functions such as catalyzing chemical reactions (enzymes), providing structural support (collagen in animals), and facilitating communication between cells (hormones). immune defense (antibodies) and in transporting molecules across cell membranes. Nucleic Acids (DNA and RNA): DNA (deoxyribonucleic acid) is the genetic material that stores the instructions for building and maintaining an organism. ◆ It consists of long chains of nucleotides, which include a sugar, phosphate group, and nitrogenous bases (adenine, thymine, guanine, cytosine). RNA (ribonucleic acid) plays a crucial role in translating these instructions into proteins by guiding protein synthesis in cells. ◆ involved in gene regulation and various cellular functions. PRELIMINARY 24-25 Lipids (Fats): hydrophobic molecules — they do not mix with water. crucial for forming cell membranes (phospholipids) that protect the cell and regulate the movement of substances in and out of the cell. store energy (fats) and act as signaling molecules (steroids). Carbohydrates: primary energy source for living organisms. Carbohydrates include sugars, starches, and fibers. They provide energy for metabolism and serve as structurQal components in cells (e.g., cellulose in plant cell walls, glycogen in animal tissues). All living systems build and maintain these macromolecules, which are far more complex than the small molecules found in non-living matter. The ability to organize these molecules into functional units is one of the key distinctions of life. ❖ Hierarchical Organization Life is organized into several levels of complexity. Starting from the smallest components like atoms and molecules, these form: Cells: The basic unit of life. Tissues: Groups of cells that work together to perform specific functions. Organs: Composed of different tissues working together (e.g., the heart, lungs). PRELIMINARY 24-25 Organ Systems: Groups of organs working in coordination (e.g., digestive system, nervous system). Organisms: Individual living entities that can carry out all life processes. Populations: Groups of the same species living in an area. Ecosystems: Interactions between different species and their environment. Each level builds on the one below it, leading to increasing complexity and emergent properties—characteristics that arise from interactions at each level that couldn’t be predicted just by looking at the lower levels. ❖ Reproduction and Variation Living organisms have the ability to reproduce, ensuring the survival of their species. Reproduction can be: Asexual: Involves a single organism producing offspring genetically identical to itself (e.g., bacteria dividing). Sexual: Involves the combination of genetic material from two parents, leading to offspring with genetic variation. Reproduction ensures that traits are passed from one generation to the next (heredity), while also introducing variations, which provide the raw material for evolution. ❖ Metabolism PRELIMINARY 24-25 Metabolism refers to the sum of all chemical reactions that occur in an organism to maintain life. These reactions can be divided into: Catabolic Reactions: Break down complex molecules into simpler ones, releasing energy (e.g., digestion). Anabolic Reactions: Use energy to build complex molecules from simpler ones (e.g., protein synthesis). These processes enable organisms to grow, reproduce, repair damage, and respond to their environment. The energy needed for metabolism is often supplied by the breakdown of nutrients like glucose, which cells convert into usable energy (ATP) through processes like cellular respiration. ❖ Development Development refers to the changes an organism undergoes from conception to maturity. It includes processes like: Growth: Increase in size and number of cells. Differentiation: Cells specialize to perform different functions. Morphogenesis: The development of an organism's shape and body structures. For example, in humans, development begins with a single fertilized egg cell, which divides and differentiates into all the specialized cells and tissues of the body. PRELIMINARY 24-25 ❖ Environmental Interaction ❖ All living organisms interact with their environment in some way. They may respond to stimuli like light, temperature, or the presence of other organisms. Animals can adapt to their surroundings, either through immediate behavioral responses or longer-term evolutionary changes. The study of these interactions is known as ecology, which looks at how organisms survive and thrive in different environments and how populations interact within ecosystems. 3. Evolution and Heredity Two major theories form the backbone of our understanding of zoology: Theory of Evolution Proposed by , the theory of evolution explains how species change over time through the process of natural selection. According to this theory: Organisms produce more offspring than can survive. Individuals within a species show variation in traits. Some traits are more favorable for survival and reproduction in a particular environment. Over time, these favorable traits become more common in the population, leading to evolutionary change. This theory helps explain the diversity of life forms and their adaptations to different environments. Chromosomal Theory of Inheritance The Chromosomal Theory of Inheritance explains how traits are passed from parents to offspring through chromosomes. Chromosomes carry genes, which are units of heredity made of DNA. During reproduction, offspring inherit a set of chromosomes from each parent, leading to a combination of traits from both. This theory, combined with Mendelian genetics, explains how traits are inherited and why offspring resemble their parents but also exhibit variation. PRELIMINARY 24-25 In summary, these fundamental biological principles—chemical uniqueness, hierarchical organization, reproduction, metabolism, development, environmental interaction, evolution, and heredity—are the cornerstones of zoological studies. They explain the processes that sustain animal life and the mechanisms through which life diversifies and adapts over time.