BIOL1020 Lecture 2 - Ecology

Ecology is the study of interactions between living organisms and their environment. This branch of biology is essential for understanding the complex relationships that sustain life on Earth, including how species interact with each other and their non-living surroundings, such as air, water, and soil.

Properties of Life

All organisms possess notable characteristics that define them as living entities:

  • Order/Organization: Living things exhibit complex organization and order, which is essential for the functioning and survival of the organism. Life forms are structured in various levels, including cells, tissues, organs, and systems.

  • Sensitivity or Response to Stimuli: Organisms respond to environmental stimuli, such as light, temperature, and chemical signals. This responsiveness is crucial for survival, as it helps organisms adapt to their surroundings and find resources.

  • Reproduction: Living organisms have the capacity to reproduce, thereby passing on genetic information to future generations. They can reproduce sexually or asexually, which contributes to the genetic diversity of populations.

  • Adaptation: Over generations, organisms undergo changes through evolution that enable them to survive and thrive in specific environments. Adaptations may include physical traits, behaviors, or metabolic processes.

  • Growth and Development: All living organisms develop according to genetically determined instructions, allowing them to grow and differentiate into specialized forms and functions.

  • Regulation/Homeostasis: Organisms actively maintain stable internal conditions (homeostasis) despite external environmental changes. For example, humans regulate body temperature to remain around 37°C regardless of external conditions.

  • Energy Processing: Organisms acquire energy from their environment to maintain metabolic processes. This includes photosynthesis in plants, where solar energy is converted to chemical energy, and consumption in animals, which rely on plants or other animals for energy.

  • Evolution: The evolutionary process influences all aspects of survival, adaptation, and interactions among organisms. Evolution occurs through natural selection, genetic drift, and mutations that lead to the development of new traits and behaviors.
    These characteristics form the basis for defining life and help biologists study living organisms systematically.

Order/Organization of Living Organisms

Living things are organized from small to large scales:

  • Cells: The basic unit of structure and function in all organisms, capable of carrying out all necessary life processes.

  • Atoms: The smallest unit of matter that join together to form molecules through chemical bonds.

  • Macromolecules: Large molecules formed from smaller units (monomers) that are crucial for cellular function, including proteins, nucleic acids, carbohydrates, and lipids.

  • Organelles: Specialized structures within cells that perform specific functions, such as mitochondria (energy production) and chloroplasts (photosynthesis).

  • Organisms: Can be unicellular (single-celled) or multicellular (complex systems with various cell types).

    • Prokaryotic Cells: Unicellular organisms that lack a membrane-bound nucleus and organelles, such as bacteria.

    • Eukaryotic Cells: More complex cells that contain a nucleus and other organelles, found in plants, animals, fungi, and protists.

Levels of Organization

Higher levels include:

  • Tissues: Groups of similar cells that work together to perform a specific function (e.g., muscle tissue, nervous tissue).

  • Organs: Collections of tissues that work together to perform complex functions (e.g., heart, lungs).

  • Organ Systems: Groups of organs that coordinate their functions (e.g., circulatory system, respiratory system).

  • Organisms: Individual living entities that may belong to various species, exhibiting their specific traits.

  • Populations: Groups of individuals of the same species residing in a specific area, interacting with each other.

  • Communities: Different populations of organisms that live together and interact in a shared environment.

  • Ecosystems: Combinations of living (biotic) and non-living (abiotic) components in a particular area, including interactions and energy flow between them.

  • Biosphere: The sum of all ecosystems, encompassing all life on Earth, characterized by its various habitats and climatic zones.

Sensitivity or Response to Stimuli

Living organisms respond to stimuli from their environment in ways that are often crucial for survival. Examples include:

  • Phototropism: Plants bending towards light.

  • Chemotaxis: Bacteria moving towards nutrients or away from harmful substances.
    Responses may be classified as:

  • Positive: Movement toward the stimulus (e.g., animals moving towards food).

  • Negative: Movement away from the stimulus (e.g., closing leaves when touched).

Reproduction

Reproduction is a fundamental characteristic of life. It occurs in two main forms:

  • Asexual Reproduction: In single-celled organisms, DNA duplications occur followed by cell division, resulting in two identical cells.

  • Sexual Reproduction: In multicellular organisms, reproduction occurs through the formation of gametes (sperm and eggs) which fuse to form a zygote, creating genetic variation in the offspring.
    Offspring inherit DNA that contains genes, ensuring similarities with parents and enabling the passing down of traits.

Adaptation and Evolution

Living organisms adapt over time to their environments through the mechanisms of evolution and natural selection. These adaptations ensure that species can cope with changing habitats and environmental pressures, which is vital for survival and reproduction in specific ecosystems. Examples include the ability of desert plants to conserve water and the camouflage of prey species to evade predators.

Growth and Development

Organisms undergo growth and development according to genetic instructions encoded in their DNA, which directs systematic differentiation and structuring throughout their lifecycle, allowing them to retain key similarities to their parent organisms.

Regulation/Homeostasis

Organisms maintain stable internal conditions despite environmental changes through processes such as:

  • Thermoregulation: Maintaining body temperature within a certain range.
    For example, polar bears possess adaptations like thick fur and a layer of fat to conserve body heat in cold climates.

  • Osmoregulation: Balancing water and solute concentrations.

Energy Processing

Organisms convert and utilize energy for metabolic activities, categorized as follows:

  • Autotrophs: Organisms that produce their own energy, such as photosynthetic plants, converting solar energy into chemical energy.

  • Heterotrophs: Organisms that consume other organisms to obtain energy, including herbivores, carnivores, and omnivores, thus engaging in complex food webs and energy transfers within ecosystems.

Levels of Study in Ecology

Ecology can be studied at several levels:

  1. Organismal Ecology: Focus on how individual organisms adapt to their habitats; for example, the Karner blue butterfly relies on wild lupine for survival.

  2. Population Ecology: Examines populations, including dynamics, growth, and factors affecting endangered species and their resilience.

  3. Community Ecology: Investigates interactions among species in communities, such as predation, competition, and mutualism.

  4. Ecosystem Ecology: Studies the flow of energy and nutrients among organisms and their environment, including the interactions between biotic and abiotic factors.

Influences of Abiotic Factors

Abiotic factors significantly impact the distribution and survival of organisms. Key abiotic factors include:

  • Solar Energy: The primary energy source for photosynthesis, influencing plant growth and, subsequently, the entire food web.

  • Temperature: Organisms have specific temperature ranges for survival (e.g., most living things struggle to survive at temperatures below 0°C or above 45°C).

  • Water: Vital for all cellular processes; variations in water availability influence the distribution of terrestrial and aquatic organisms. Organisms in freshwater being surrounded by water of a lower solute concentration are constantly under the threat of water rushing into their cells as a result of osmosis (movement of water from low to high concentration). As a result, they have developed adaptations which ensure that solute concentrations of their bodies remain at levels which appropriate for their survival, such as dilute urine excretion. Marine organisms, on the other hand, are surrounded by salt water with a higher solute concentration than. such organisms, and thus, under the threat of water rushing out of their cells as a result of osmosis. These organisms have developed adaptations which facilitate their ability to retain water as well as release solutes into the environment. Marine iguanas (Amblyrhynchus cristatus), for example, sneeze out high-salt water vapor so as to maintain solute concentration at an acceptable level while they swim in the ocean

  • Soil and Nutrients: The physical and chemical properties of soil affect plant growth and distribution; plants extract essential nutrients, while animals obtain energy and nutrients by consuming plants or other animals. Understanding these influences is essential for conservation and habitat management strategies.