Plant Tropisms, Nasties, and Reproductive Strategies
Types of Tropisms
Tropisms are directional growth responses of a plant to environmental stimuli.
Phototropism
Response of a plant to light variation. It is manifested by a curvature of the plant. Stems exhibit positive phototropism (growing towards light), and roots exhibit negative phototropism (growing away from light).
Hydrotropism
Response of a plant to a stimulus based on water. Roots show positive hydrotropism, growing towards water sources.
Thigmotropism
Response to stimuli from touch or physical
Read MorePhotosynthesis and Chemosynthesis in Autotrophs
Photosynthesis
All cells can obtain energy from the oxidation of organic molecules (such as glucose). Autotrophic cells must synthesize these molecules before they can catabolize them: autotrophic metabolism. The process of synthesizing biomolecules from CO2 and H2O as initial substrates, using sunlight as an energy source, is called photosynthesis.
- Overall reaction: 6CO2 + 6H2O + light → C6H12O6 + 6O2
- Photosynthetic organisms: Green plants, algae (green, red, brown), cyanobacteria, and some bacteria
Understanding the Peripheral and Central Nervous Systems
The Peripheral Nervous System
The peripheral nervous system is responsible for connecting the sensory organs and nerves with the effector organs. It consists of nerves, which are like strands formed by several axons. To prevent the passage of current, the axons are electrically isolated from each other by the myelin sheath.
The nerves are classified as:
- Sensory nerves: transmit sensory information from the sensory organs.
- Motor nerves: send commands to the effector organs.
- Mixed nerves: contain axons
Cell Biology: Levels of Organization, Biomolecules, and Functions
Levels of Organization in Biology
Levels of organization: Atom > Molecule > Organelle > Cell > Tissue > Organ > Organ system > Organism
Bioelements and Biomolecules
Bioelements: Chemical elements that make up living things. Bioelements join together to form biomolecules. Two types:
Inorganic Biomolecules
Inorganic biomolecules include water and mineral salts.
Water is the most abundant substance found in living things, making up about 65% of the human body. Mineral salts can be found
Read MoreHuman Digestive and Respiratory Systems: Health & Function
Digestive System: Function and Processes
Digestion takes place in the organs of the digestive tract.
Mouth
Digestion begins here through the mechanical actions of the teeth and tongue, and the chemical action of the enzyme amylase, present in saliva. Amylase transforms complex carbohydrates into simple sugars. This transformation contributes to the formation of the bolus.
Stomach
Gastric digestion of the bolus occurs here. The stomach walls secrete gastric juices that contain hydrochloric acid and enzymes
Read MoreOrigin of Life: Pasteur, Darwin, Miller & Evolution Explained
Act II: The Life
Scene I: The Early Word
What role did Pasteur and Darwin play in explaining the origin of life?
Pasteur demonstrated that microscopic germs are ubiquitous. He conducted an experiment isolating meat and vegetable broth, boiling it to sterilize it, and concluded that life does not arise spontaneously but is a process that takes time.
Darwin’s principle of evolution of species posits that species are modified by natural selection, where nature selects the fittest for survival.
What did
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