There are 2 types of transport mechanisms that involve the movement of materials across the cellular membrane:
1. Passive Transport Mechanisms which is the movement of materials that does not require energy. Instead the movement relies on the permeability of the cell. Under this are three kinds of passive transport mechanisms:
a. Simple Diffusion:
- the movement of materials from a region of higher concentration to lower concentration. No external energy is necessary for the movement. The materials supply the energy themselves.
b. Facilitated Diffusion:
- This differs from simple diffusion because the movement is facilitated by proteins that make up the structure of the membrane. The proteins include channel proteins that allow ions and smaller molecules to cross the membrane. The other protein are the carrier proteins, which bind to materials like sugar molecules and move it across the membrane.
c. Osmosis:
- This is the diffusion of water across the membrane. Osmosis moves water from regions where there are more water molecules of water per volume to regions where there are less water molecules per volume.
2. Active transport on the other hand is a movement mechanism that requires energy. It uses the energy to send materials against the direction it is coming from through simple diffusion. This mechanism is used in a way to keep unwanted ions or other materials out of the cell.
Explanation:
Organisms don’t have to only reproduce sexually or only reproduce asexually - some animals do both!
When conditions are good, such organisms will reproduce asexually because it is easier. For example, starfish (by fragmentation), slime molds, and water fleas/daphnia (by parthenogenesis) all reproduce asexually when there is plenty of food, minimal predators, and not too much crowding of individuals of the same species.
When conditions worsen (less food, too many individuals, etc), they may switch to sexual reproduction in order to add genetic variation to their population and ensure survival through difficult times.
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I believe that the answer is: Most organisms are made up of one or more cells
Cell Theory was first developed in 1839 by Schleiden and Schwann, they stated that all organisms are composed of one or more cells.
