Biology 16 Flashcards
Diagram of kidney
Nastic response
A nastic response, also known as a nastic movement, is a non-directional response by a plant to a stimulus. Unlike tropic responses, which involve growth towards or away from a stimulus, nastic responses are independent of the direction of the stimulus. Instead, they involve changes in the shape or orientation of plant organs in response to specific environmental cues, such as changes in light, temperature, humidity, or touch.
Nastic responses are typically rapid and reversible and can involve various plant organs, including leaves, petals, stems, and roots. Examples of nastic responses include the closing of petals in certain flowers at night (nyctinasty), the folding of leaves in response to touch (thigmonasty), and the opening and closing of stomata in response to changes in light intensity (photonasty).
Nastic responses allow plants to adapt to changes in their environment and optimize their growth and survival. They are controlled by changes in turgor pressure, hormone levels, and ion fluxes within plant cells and tissues.
Dipping a decolorized leaf in hot water during the starch test
Dipping a decolorized leaf in hot water during the starch test serves to soften the leaf tissue and facilitate the extraction of starch from the chlorophyll. Here’s why it’s done:
1. Softening the Leaf Tissue: Heating the leaf in hot water helps to soften the cell walls and tissue structure of the leaf. This makes it easier to break down the cells and release the starch granules trapped inside. 2. Denaturing Enzymes: Hot water can also denature enzymes present in the leaf tissue that may interfere with the detection of starch. Enzymes such as amylase, which are involved in starch metabolism, may break down starch molecules into simpler sugars. Heating the leaf inactivates these enzymes, preventing them from affecting the test results. 3. Enhancing Starch Extraction: By softening the leaf tissue and denaturing enzymes, hot water facilitates the extraction of starch from the leaf. This allows the starch granules to be more readily released into the surrounding solution, making them available for detection with iodine solution.
Overall, dipping the decolorized leaf in hot water helps to optimize the conditions for detecting the presence of starch and ensures accurate results in the starch test.
Light-Dependent Reactions (Light Stage):
- Light-Dependent Reactions (Light Stage):
• Absorption of Light Energy: Chlorophyll and other pigments in the thylakoid membranes of chloroplasts absorb light energy from the sun.
• Water Splitting (Photolysis): Light energy is used to split water molecules (H2O) into oxygen (O2), protons (H+), and electrons (e-). This process releases oxygen as a byproduct.
• Generation of ATP: The energy from the excited electrons is used to pump protons across the thylakoid membrane, creating a proton gradient. This gradient drives the synthesis of ATP through ATP synthase.
• Generation of NADPH: The excited electrons are transferred to NADP+ (nicotinamide adenine dinucleotide phosphate), along with protons, to form NADPH, which is a reducing agent used in the Calvin cycle.
Light-Independent Reactions (Dark Stage or Calvin Cycle):
Light-Independent Reactions (Dark Stage or Calvin Cycle):
• Carbon Fixation: Carbon dioxide (CO2) from the atmosphere is fixed into organic molecules. The enzyme ribulose bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the addition of CO2 to ribulose bisphosphate (RuBP), forming an unstable six-carbon compound that immediately breaks down into two molecules of 3-phosphoglycerate (3-PGA).
• Reduction: ATP and NADPH generated during the light-dependent reactions are used to reduce 3-PGA to glyceraldehyde-3-phosphate (G3P), a three-carbon sugar.
• Regeneration of RuBP: Some of the G3P molecules are used to regenerate RuBP, ensuring the continuous operation of the Calvin cycle.
• Production of Carbohydrates: The remaining G3P molecules can be used to synthesize glucose and other carbohydrates, which are essential for plant growth and metabolism.
Chlorofluorocarbons (CFCs)
Chlorofluorocarbons (CFCs) are synthetic organic compounds that were first developed in the early 20th century for use as refrigerants, propellants in aerosol sprays, solvents, and foam-blowing agents. They are composed of carbon, chlorine, and fluorine atoms.
While CFCs are human-made chemicals, they do not have a natural origin. They were first synthesized by scientists as industrial chemicals in the 1920s and were widely used in various applications due to their stability, non-toxicity, and non-flammability.
The environmental impact of CFCs became a major concern when it was discovered that they have destructive effects on the ozone layer in the Earth’s stratosphere. When released into the atmosphere, CFCs can eventually reach the stratosphere, where they are broken down by ultraviolet (UV) radiation, releasing chlorine atoms. These chlorine atoms then catalytically destroy ozone molecules (O3), leading to the depletion of the ozone layer.
Due to their significant role in ozone depletion and their contribution to global warming as greenhouse gases, the production and use of CFCs have been largely phased out under the Montreal Protocol, an international treaty aimed at protecting the ozone layer. Since the 1990s, alternative compounds with less harmful environmental impacts have been developed to replace CFCs in most applications.
The outermost tissue of herbaceous plants is the
The outermost tissue of herbaceous plants is the epidermis. The epidermis is a single layer of cells that covers the entire aerial surface of the plant, including the stems, leaves, flowers, and young roots. Its primary function is to protect the plant from mechanical damage, pathogens, and excessive water loss, while also allowing for gas exchange and the absorption of water and nutrients. In some specialized structures, such as leaves, the epidermis may also contain specialized cells, such as stomata for gas exchange and trichomes for defense or reducing water loss.
Homodont dentition
Homodont dentition refers to a type of tooth arrangement where all teeth are similar in shape and size. This type of dentition is commonly found in animals such as fish and reptiles, where teeth are used for grasping and holding prey rather than chewing.
Mouth brooding behavior in tilapia, where the parent fish carries eggs or fry in their mouth for protection, serves several important purposes:
Mouth brooding behavior in tilapia, where the parent fish carries eggs or fry in their mouth for protection, serves several important purposes:
1. Protection: Mouth brooding provides physical protection for the eggs or fry against predators, ensuring a higher survival rate. 2. Environmental Adaptation: It helps tilapia species adapt to various environmental conditions, especially in areas with fluctuating water levels or poor water quality. 3. Parental Care: Mouth brooding allows for direct parental care, as the parent fish can closely monitor the development of the offspring, ensuring their health and safety. 4. Resource Conservation: By carrying the offspring in their mouth, tilapia conserve energy and resources that would otherwise be spent on building and maintaining nests or other forms of protection. 5. Increased Reproductive Success: Mouth brooding behavior can lead to higher reproductive success by increasing the chances of survival for the offspring, ultimately contributing to the long-term viability of the species.
Perilymph
Balance
The relationship between termites and protozoa in their intestine
The relationship between termites and protozoa in their intestine is a symbiotic one, where both organisms benefit. Termites rely on protozoa to help digest cellulose, a complex carbohydrate found in wood and plant material, which is otherwise indigestible to them.
The termite provides a suitable environment for the protozoa to thrive in its gut, offering warmth, protection, and a constant food source. In return, the protozoa produce enzymes that break down cellulose into simpler sugars that the termite can absorb and utilize for energy.
This mutualistic relationship allows termites to efficiently extract nutrients from their wood-based diet, while the protozoa gain a stable habitat and a constant food supply.
Denitrifying bacteria
Denitrifying bacteria are a type of bacteria that play a key role in the nitrogen cycle by converting nitrate (NO3-) and nitrite (NO2-) into nitrogen gas (N2) or nitrous oxide (N2O). This process, known as denitrification, occurs in anaerobic conditions where oxygen is limited or absent.
Denitrifying bacteria help regulate the nitrogen balance in ecosystems by returning nitrogen gas to the atmosphere, thereby completing the nitrogen cycle. This process is essential for maintaining healthy soil and water quality, as excessive nitrate levels can lead to environmental problems such as eutrophication and groundwater contamination. Denitrifying bacteria are particularly important in agricultural systems, where they can help mitigate the impacts of nitrogen fertilizers on the environment.
Putrefying bacteria
Putrefying bacteria are a type of bacteria that play a crucial role in the process of putrefaction, which is the decomposition of organic matter. These bacteria thrive in anaerobic (oxygen-deprived) environments and are responsible for breaking down proteins in dead organisms, releasing foul-smelling gases such as ammonia, hydrogen sulfide, and methane in the process.
Putrefying bacteria contribute to the decay of organic matter, helping to recycle nutrients back into the ecosystem. However, their activity is also responsible for the unpleasant odor associated with decomposing organic material.
