Characteristics of Living Things

Characteristics of Life

Biology

  • Biology is the study of life. Examples of biology fields include:
    • Entomology: Insect biology
    • Histology: Tissue biology
    • Ornithology: Bird biology
    • Ichthyology: Fish biology

Characteristics of Living Things

  • There are 8 characteristics of life, and living things must demonstrate all eight.
  • Living things include:
    1. Made up of cells.
    2. Levels of organization.
    3. Reproduction (sexual or asexual).
    4. Growth.
    5. Based on a universal genetic code (DNA).
    6. Response to the environment.
    7. Require energy.
    8. Adapt and evolve (as a group).
    9. Homeostasis.

Cells

  • Life is composed of tiny living units called cells.
  • Cells are the smallest unit of an organism that can be considered “alive.”
  • Organisms can be unicellular (made of 1 cell) or multicellular (made of more than 1 cell).
  • Sponges have specialized cells, such as myocytes (muscle cells) for movement.

Levels of Organization

  • Multicellular organisms have an organization beyond the cellular level.
  • The levels of organization include:
    • Biosphere: The part of Earth that contains all ecosystems.
    • Ecosystem: Community and its nonliving surroundings.
    • Community: Populations that live together in a defined area.
    • Population: Group of organisms of one type that live in the same area.
    • Organism: Individual living thing.
    • Groups of Cells: Tissues, organs, and organ systems.
    • Cells: Smallest functional unit of life.
  • Sponges have cells organized to form tissue with specific functions.

Reproduction

  • Living things reproduce to carry on their species.
  • Types:
    • Sexual Reproduction: The mixing of genetic material from 2 members of the same species.
    • Asexual Reproduction: Offspring are genetically identical to the parent. No mixing of genetic material.
  • Asexual reproduction examples: plants and bacteria split into two organisms (budding); offspring are genetically identical to parent.
  • Sexual reproduction examples: some plants and animals reproduce through another member of their species; offspring are not genetically identical to parent/s: a unique blend of recombined DNA.
  • Sponges can reproduce asexually (by branching off) or sexually (as hermaphrodites producing sperm and eggs).

Growth

  • Living things grow over their lifetimes.
  • Single-celled organisms increase their volume, and multicellular organisms add to the number of cells.
  • During development, a single egg divides again and again via mitosis.
  • New cells can be created and differentiate to perform certain functions for the organism as time passes
  • A new sponge will develop and grow into a mature sponge.

Genetic Code

  • All organisms store complex information in DNA.
  • DNA/RNA are the codes or sequences that get translated into all types of proteins
  • DNA is found in the nucleus of eukaryotic organisms.
  • Sponges have DNA contained in their sex cells.

Response to the Environment

  • Living things react to stimuli and interact with their surroundings.
  • Stimuli can be abiotic (non-living) or biotic (living) factors.
  • A stimulus is a signal to which an organism responds.
  • Responses can occur at the cellular level through homeostasis, or as a complex set of responses called behavior.
  • Lower organisms undergo types of taxis (e.g., phototaxis, hydrotaxis).
  • Higher organisms undergo behaviors often using chemical messengers (hormones).
  • Sponges can sense predators and respond by contracting their surface layer.

Energy

  • Living organisms require energy, in the most basic form of ATP.
  • Heterotrophs: Obtain energy through the breakdown of food and nutrients.
  • Autotrophs Use photosynthesis & chemosynthesis – Energy obtained through inorganic sources.
  • Metabolism: The total sum of all chemical reactions in the body.
  • Sponges move by contracting their muscle cells, which requires energy.
  • Some sponges can make their own food through photosynthesis, others get their food by absorbing nutrients from the water.
  • Sponges absorb nutrients by allowing water to flow through them.
  • The sugars react with oxygen, which is absorbed from the water, to produce energy for the sponge, waste products are removed by the water.

Adapt and Evolve

  • Over many generations, groups of organisms typically evolve or change over time.
  • Occurs via changes in DNA sequences (mutations) that code for proteins (known as traits)
  • Beneficial mutations will survive and reproduce in the changing environment and pass them on to future offspring.
  • Organisms and Species adapt to their environment in order to survive.
  • Adaptation occurs to best suit the habitat, and may or may not be reversible.

Homeostasis

  • All organisms maintain a stable internal balance, also known as homeostasis.
  • This ensures that body systems work at their best levels. (Temperature, pH, Water/Osmotic Pressure, Salt balance)
  • Homeostasis is accomplished by various types of feedback loops.
    • Negative Feedback loop: Reducing the output or activity of any organ or system back to its normal range of functioning (Shivering/Sweating, Blood Pressure).
    • Positive Feedback Accelerates or enhances the output created by a stimulus that has already been activated (Oxytocin release during birth).