Biological Definitions: Nutrition, Respiration, and Circulation
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Fundamentals of Biological Processes
Nutrition and Metabolism
- Heterotrophic Nutrition
- Organisms that obtain organic matter from other living beings through food.
- Aerobic Respiration
- The process of breaking down the glucose molecule using oxygen.
- Fermentation
- A process of molecular decomposition that occurs without oxygen (anaerobic process).
- Glycogen
- A molecule present in animal cells used for energy reserves.
Classification of Heterotrophs
Heterotrophs are classified based on their primary food source:
- Herbivores: Organisms that feed exclusively on plants.
- Carnivores: Organisms that feed on other animals.
- Omnivores: Organisms that feed on both plants and other animals.
- Suspensivores: Organisms that feed on microorganisms and organic matter obtained by filtering water.
- Saprophytes: Organisms that feed on the remains of living organisms, such as branches, dead leaves, carcasses, or droppings.
- Parasites: Organisms that feed on a plant or animal while it is still alive, often causing damage.
Digestion and Invertebrates
- Digestion
- The process of decomposing organic food molecules into nutrients—smaller molecules that can be incorporated and used by cells.
Cnidarians
Cnidarians are a group of marine invertebrates bearing stinging cells. They can be: jellyfish or polyps.
Respiratory Systems and Breathing
Different organisms utilize various methods to obtain oxygen:
- Skin (Cutaneous Respiration)
- Amphibians and many invertebrates obtain oxygen directly from the outside through their skin, which is very thin and moist. This process is called cutaneous respiration.
- Gills
- Fish and some invertebrates (such as aquatic amphibians) absorb oxygen dissolved in water through their gills—organs shaped like pens or sheets through which water circulates.
- Tracheae
- Terrestrial arthropods obtain oxygen by circulating air through a system of branching tubes that run throughout the body. These tracheae may come to occupy half the volume of the body.
- Lungs
- Terrestrial vertebrates and some invertebrates have internal cavities that fill with air. To increase the surface area for oxygen absorption, the lungs are usually divided into multiple chambers or alveoli.
Circulatory System
- The Heart
- The organ that pumps blood through blood vessels.