Earth and Life Sciences - Introduction to Life Science

Concept of Life

Introduction

• Etymology of Biology: Derived from the Greek words bios (meaning life) and LOGOS (meaning study). It literally translates to the study of life.

• Cellular Nature of Life: All living things are composed of cells.

  • Unicellular Organisms: Consist of a single cell that carries out all vital life processes.

  • Multicellular Organisms: Composed of many cells that perform specialized and specific functions.

Characteristics of Life

Response to Stimuli

• Definition: The ability of living things to react to environmental factors.

• Environmental Factors: Includes light, temperature, pressure, chemicals, and gravity.

Metabolism

• Definition: The sum total of all chemical reactions occurring within an organism.

• Types of Metabolism:

  • Catabolism: The breakdown of larger, complex molecules into simpler ones.

  • Anabolism: The synthesis of larger, complex molecules from simpler ones.

Reproduction

• Definition: The ability of living organisms to produce new individuals that closely resemble them.

Growth and Development

• Definition: The capacity of organisms to grow and develop over time.

• Mechanisms: Organisms develop by either growing new parts or increasing in physical size.

Homeostasis

• Definition: The process of maintaining a stable and specific internal environment despite external changes.

• Regulated Parameters: Organisms regulate internal conditions such as pH, temperature, and electrolyte concentrations to survive.

• Consequences: Inability to regulate the internal environment leads to death.

Adaptation

• Definition: A primary survival mechanism wherein living organisms adjust to changing environmental conditions over time.

Organization

• Structural Hierarchy: Living organisms exhibit a complex structural hierarchy:

  • Organisms are composed of cells.

  • Cells are composed of specialized organelles.

  • Organelles (such as the cell membrane) are constructed from macromolecules.

  • Macromolecules (such as fats) are composed of individual atoms (such as carbon, hydrogen, and other elements).

Viral Classification: Is a Virus Alive?

• Living Status: Viruses are not considered living organisms because they lack key characteristics of life.

• Genetic Material vs. Autonomy: Viruses possess genetic material, but they cannot reproduce independently.

• Reproductive Mechanism: Viruses reproduce strictly by infecting host cells, utilizing the host cell's ribosomes, ATP, enzymes, and other molecular structures to assemble new virus particles.

Origin of Life

Special Creation Theory

• Core Concept: Proposes that everything in the universe was created by a Supreme Being, with whom nothing is impossible.

• Scriptural Reference: Documented in the Bible in Genesis 1:1–28 and Genesis 2:1–4.

Spontaneous Generation

• Core Concept: The historic theory that living organisms can spontaneously arise from non-living matter.

• Experimental Refutations:

  • Francesco Redi: Placed snake meat, fish, and a slice of veal in flasks covered with muslin cloth. He demonstrated that maggots developed on meat only if flies were able to lay eggs directly on it.

  • Lazzaro Spallanzani: Demonstrated that when meat juices were boiled for three-quarters of an hour and subsequently sealed, no life developed.

  • Louis Pasteur: Designed a swan-neck culture flask that allowed air to enter through a curved tube while causing airborne bacteria to settle by their own weight in the curve. No life appeared in the sealed flask, disproving spontaneous generation.

Biogenetic Theory

• Core Concept: Proposes that living things can only arise from pre-existing living things.

• Scientific Basis: Validated following the invention of the microscope and subsequent advancements in biological science.

• Examples:

  • Sexual reproduction involves the fusion of an egg cell and a sperm cell to form a zygote, which develops into an organism.

  • Microorganisms such as bacteria reproduce to give rise to additional bacteria.

Beneath the Ice Theory

• Environmental Context: Billions of years ago, Earth's oceans were covered by ice hundreds of meters thick due to a weaker sun.

• Mechanism: Proposes that the thick ice protected delicate organic compounds from harsh radiation and destructive impacts, allowing them to interact and give rise to life.

Electric Spark Theory

• Experimental Basis: Demonstrates that electricity can synthesize simple sugars and amino acids from basic elements present in the atmosphere.

• Mechanism: Suggests that lightning discharging through rich volcanic gas clouds provided the energy needed to initiate the formation of organic molecules.

Panspermia (Cosmozoic Theory)

• Core Concept: Proposes that life on Earth originated from extraterrestrial sources, arriving via meteorites, rocks, and space debris carrying highly resistant spores known as cosmozoa.

Submarine Hydrothermal Vents

• Environmental Context: Deep-sea hydrothermal vents harbour vast and diverse ecosystems.

• Mechanism: The nutrient-rich aquatic environment, saturated with reactive gases and natural catalysts, created ideal conditions to spawn early life forms.

Hylomorphism

• Philosophical Concept: Asserts that everything in the universe consists of matter united with a soul (which represents life).

• Three Types of Souls:

  • Vegetative Soul

  • Animal Soul

  • Rational Soul

Miller-Urey Experiment

• Researchers: Conducted by Stanley Miller and Harold Urey.

• Objective: Simulated primordial Earth atmospheric conditions in a closed laboratory system to demonstrate the spontaneous abiotic formation of early organic molecules.

Endosymbiotic Theory

• Core Concept: Explains the evolution of eukaryotic cells from prokaryotic ancestors.

• Mechanism: Free-living prokaryotic cells were engulfed by or entered ancestral eukaryotic cells, establishing a symbiotic relationship and becoming permanent intracellular organelles.

Unifying Themes in the Study of Life

Biological Systems

• Scope: Applies across all structural levels of biology, from the biosphere down to molecular interactions inside individual cells.

• System Properties: A system exhibits emergent properties based on the structural arrangement and functional interactions of its parts.

• Example: A forest ecosystem functions as a biological system.

Cellular Basis of Life

• Hierarchy of Organization in Multicellular Organisms:

  • Cellular Level: The basic structural and functional unit of life.

  • Tissue Level: Groups of similar cells organized together to perform a specific function.

  • Organ Level: Combinations of different tissue types working together to form a distinct structure (e.g., the brain composed of nerve tissue and supporting tissues).

  • Organ System Level: Multiple organs working in tandem to carry out major physiological functions (e.g., the nervous system composed of the brain, spinal cord, and nerves).

Reproduction and Inheritance

• Fundamental Principle: "Like begets like."

• Genetic Inheritance: Offspring inherit discrete units of genetic information called genes from their parents, which account for familial traits and resemblance.

• Human Reproduction Example: Fusion of a maternal egg cell and a paternal sperm cell forms a fertilized zygote containing a combined set of DNA from both parents.

Environmental Interactions

• Interconnectedness: No organism exists in complete isolation. As components of an ecosystem, organisms continuously interact with both biotic and abiotic elements of their surroundings.

• Photosynthetic Example: Plants require three environmental inputs (carbon dioxide, water, and sunlight) to carry out photosynthesis.

Energy and Life

• Energy Dependence: Biological work depends on a continuous supply of energy, which is converted through chemical reactions.

• Energy Flow: Energy enters an ecosystem as sunlight and exits as thermal energy (heat).

Regulation

• Definition: The capacity of organisms to regulate internal biological mechanisms.

• Homeostasis: Internal regulatory mechanisms allow organisms (such as birds and mammals maintaining body temperature) to preserve internal stability despite external fluctuating environments.

Evolution and Diversity of Life

• Temporal Changes: Explains genetic and physical changes in populations of organisms over extended periods.

• Natural Selection: Organisms acquire beneficial structural or physiological adaptations over time in response to environmental pressures via natural selection.

• Diversity & Fossil Record: The transmission of modified inherited traits across generations explains the past and present diversity of life as preserved in the fossil record.

Scientific Inquiry

• Definition: The systematic process of raising questions about the natural world and conducting structured observations or experiments to find potential answers.