characteristics of life

Key Concepts in Biology

Adaptation

  • Definition: An inherited trait that enhances the survival and reproduction of a species.

Autotrophs and Heterotrophs

  • Autotroph: Organisms that produce their own food through processes like photosynthesis. Examples include plants and algae (plant-like protists).

  • Heterotroph: Organisms that cannot synthesize their own food and rely on other organisms for nutrition.

Cell Theory

  • Cell: The basic structural and functional unit of all living organisms.

  • Cell Theory: States that all cells originate from pre-existing cells.

  • Multicellular vs. Unicellular:

    • Multicellular: Organisms composed of multiple cells.

    • Unicellular: Organisms composed of a single cell (e.g., bacteria).

Metabolism and Energy

  • Metabolism: The total of all chemical and physical processes through which living things obtain energy from food.

  • Energy in Living Organisms: Energy is crucial for processes like cellular respiration, which utilizes ATP (adenosine triphosphate).

Organic Compounds

  • Definition: Compounds primarily made of carbon that are crucial for life.

Stimulus and Response

  • Stimulus: A change in the internal or external environment that leads to a reaction or a response from the organism.

  • Response: The action taken by an organism in reaction to a stimulus.

Spontaneous Generation

  • Definition: An outdated theory that suggested living organisms arise directly from non-living matter.

Cellular Structures

Cell Walls and Membranes

  • Cell Wall: The outermost structure present in plants, bacteria, and fungi, providing support and protection.

  • Cell Membrane: A semi-permeable membrane that regulates the substances entering and exiting the cell.

Organelles

  • Mitochondria: The site of cellular respiration, converting nutrients into energy.

  • Ribosomes: The location of protein synthesis, found in all cell types.

  • Centriole: An organelle specific to animal cells, plays a role in cell division.

  • Nucleus: The central part of a cell; houses genetic material.

  • Chloroplasts: Organelles found only in plant cells that are responsible for photosynthesis.

Photosynthesis

  • Process Overview: Plants convert light energy into chemical energy.

    • Light Reaction: Occurs in chloroplasts where water splits, releasing oxygen.

    • Dark Reaction: Utilizes carbon dioxide to synthesize glucose.

  • Stomates: Openings in leaves that facilitate gas exchange, allowing oxygen to be released.

Blood Cells

  • Red Blood Cells: Mature cells devoid of a nucleus, primarily responsible for transporting oxygen through hemoglobin.

  • White Blood Cells: Cells with a nucleus that play a key role in the immune response by targeting infected or harmful cells.