Biology: Nutritional Strategies & Organization Levels

How Organisms Get Their Food

• Fungi digest their food externally by absorption.
• Photosynthetic plants produce their own food.
• Animals ingest their food.

Levels of Biological Organization

• Atoms: The most basic unit of matter.
• Molecules: Groups of atoms.
• Organelles: Membrane-bound compartments within cells with specialized functions
• Cells: The basic unit of life.
• Tissues: Groups of similar cells working together to perform a specific function.
• Organs: Structures comprising two or more tissues with a specialized role.
• Organ Systems: Groups of organs working together to perform a specific function.
• Organisms: An individual living entity able to reproduce, grow, maintain homeostasis, and respond to stimuli.
• Population: All individuals of the same species interbreeding within a specific area.
• Community: An array of different populations in a particular ecosystem.
• Ecosystem: All the organisms (communities) living within a specific area.
• Biosphere: All the environments (ecosystems) on Earth that support life.

Acquiring Materials and Energy

• Food provides nutrients, which are used as building blocks or for energy.
• Metabolism refers to the sequence of chemical reactions that occur when cells use nutrient molecules.
• The Sun is the ultimate source of energy for life on Earth.
• Photosynthesis captures solar energy and converts it into chemical energy.

Homeostasis

• Homeostasis is the ability of an organism to maintain a balanced internal state.
• For life to continue, factors like temperature, moisture levels, and acidity must stay within a certain range for each organism.
• Control mechanisms like the release of stored sugar by the liver help maintain homeostasis.

Behavior

• Multicellular organisms exhibit more complex responses than single-celled organisms.
• Responses often involve movement, like plants turning towards the sun.
• An organism's behavior helps it maintain homeostasis, search for resources, and compete for:
  • Energy
  • Nutrients
  • Shelter
  • Mates

Reproduction

• Life only arises from existing life.
• All living organisms reproduce to create new organisms like themselves.
• Bacteria and protists reproduce asexually by splitting.
• Most multicellular organisms reproduce sexually by combining sperm and egg to form an embryo.
• Reproduction involves passing on genes to the next generation.
• Mutations (changes) in DNA can also be passed on, contributing to diversity.

Adaptation and Biodiversity

• Adaptation: Modifications that improve an organism's ability to function in its environment.
• Examples of Adaptation:
  • Penguins have thick, waterproof feathers to live in aquatic environments.
  • Camels have wide feet for walking on sand, long eyelashes, and thin nostrils for desert survival.
• All living organisms share a common ancestor — the first cell.

Organizing Diversity: Taxonomy

• Taxonomy: The practice of identifying and grouping organisms based on specific rules.
• Taxonomic Hierarchy: The classification system used to organize organisms from least inclusive (species) to most inclusive (domain) :
  • Species: A group of interbreeding individuals.
  • Genus: A group of closely related species sharing many characteristics.
  • Family: A group of related genera sharing general characteristics.
  • Order: A group of related families.
  • Class: A group of related orders.
  • Phylum: A group of related classes.
  • Kingdom: A group of related phyla.
  • Domain: The highest level of classification, grouping related kingdoms.

Linnaean Taxonomy

• Carolus Linnaeus developed binomial nomenclature, which gives each species a two-part name.
• The first part is the genus, and the second part is the specific epithet.
• The scientific name is written in italics, with the genus capitalized.
• Examples:
  • Lilium canadense (Canadian Lily)
  • Lilium bulbiferum (Bulb-bearing Lily)
• The specific epithet alone does not provide meaning, while the genus name refers to a group of related species.
• The genus can be abbreviated to a single letter when used with the specific epithet (e.g., L. bulbiferum).

Reasons for Scientific Names

• Common names vary between languages and locations, causing confusion.
• Scientific names provide a universal, standardized naming system.
• Latin is used because it is a stable, unchanging language.

The Three-Domain System

• The Three-Domain System recognizes three main evolutionary lineages:
  • Domain Bacteria:
    • Prokaryotic unicellular organisms found everywhere.
    • Diverse in structure and biochemistry.
    • Most are heterotrophic and break down organic matter.
  • Domain Archaea:
    • Prokaryotic unicellular organisms.
    • Distinguishable from bacteria by differences in rRNA sequences, plasma membranes, and cell walls.
    • Adapted to extreme environments (e.g., salty, hot, or acidic).
  • Domain Eukarya:
    • Organisms with membrane-bound nuclei.
    • Four major groups:
      • Protists: Unicellular to multicellular, some photosynthetic (e.g., algae).
      • Fungi: Decomposers, like molds and mushrooms.
      • Plants: Multicellular photosynthetic organisms.
      • Animals: Multicellular organisms that ingest and process food.

Natural Selection

• Natural selection drives adaptation, where environmental pressures select for advantageous traits to be passed to the next generation.
• Example:
  • A mutation causing a plant to produce hairy leaves might protect it from deer, allowing it to survive better and reproduce.
• Natural selection leads to evolutionary change over time.

Biodiversity

• Biodiversity: The variety of life on Earth, encompassing a vast array of living organisms, their genetic differences, and the ecosystems they form. This concept includes:
  • Species richness: This refers to the total number of different species present in a given area or ecosystem. A high level of species richness often indicates a healthy ecosystem, as it reflects various niches that species occupy, contributing to ecological roles.
  • Genetic diversity: This aspect highlights the variations in genetic makeup among individuals within a species. High genetic diversity is crucial for a population's adaptability to changing environmental conditions, disease resistance, and overall resilience.
  • Ecosystem diversity: This refers to the variety of ecosystems in a given area, including different habitats such as forests, wetlands, grasslands, and oceans. Each ecosystem supports diverse communities of organisms, contributing to the overall health of the planet.
• Biodiversity is essential for ecosystem stability and function, as it enhances productivity, promotes resilience against environmental changes, and supports ecosystem services that benefit humanity, such as pollination, filtration of water, and carbon storage.
• Extinction: The permanent loss of a species or a higher taxonomic group, which can have cascading effects on ecosystems. The extinction of species can disrupt food webs, leading to further declines in biodiversity.
• Human activities are causing a rapid rate of extinction, approximately 400 species lost every single day. Major factors include habitat destruction, pollution, climate change, and exploitation of resources.
• Mass extinction events, such as the one that led to the demise of the dinosaurs around 66 million years ago, have dramatically reshaped the Earth's biodiversity in the past and serve as a reminder of the balance of life.
• The preservation of ecosystems is a crucial bioethical issue, emphasizing the responsibility of humans to protect and conserve biodiversity for future generations and maintain the integrity of the planet's ecological systems.