CXC Past paper question Flashcards
TWO factors that may affect the rate of transpiration of the potted plant.
Humidity, Temperature, Soil Moisture, Light Intensity
Discuss how transpiration helps plants to move water from their roots to their
leaves.
Transpiration is the process by which plants lose water through small pores on their leaves called stomata. This process creates a negative pressure in the water column in the xylem tissue, which drives the upward movement of water from the roots to the leaves. The cohesive and adhesive forces in water allow it to move upward through the xylem tissue, creating a continuous flow of water from the roots to the leaves.
While absorbing water from the soil, plants absorb mineral salts such as magnesium, calcium and nitrogen. State ONE role of magnesium and ONE role of calcium in plants.
One role of magnesium in plants is its involvement in the formation of chlorophyll, the pigment responsible for photosynthesis.
One role of calcium in plants is its role in cell wall formation and structure. Calcium helps to stabilize cell walls by linking pectin molecules together, which helps to give the cell wall its rigidity and strength. Calcium also plays a role in the regulation of many cellular processes, including enzyme activity
Nitrogen is used by plants to make protein. Suggest TWO reasons why plants need
protein.
Energy storage and transport: Proteins can also serve as a source of energy storage and transport in plants.
Structural role: Proteins are important structural components of plant cells, tissues, and organs.
Suggest TWO reasons why carbon dioxide is described as a greenhouse gas.
It has the ability to trap heat in the atmosphere by absorbing and re-emitting infrared radiation, which contributes to the Earth’s natural greenhouse effect.
Human activities such as burning fossil fuels and deforestation have led to an increase in atmospheric CO2 concentrations, which has enhanced the greenhouse effect and contributed to global warming and climate change.
With reference to the carbon cycle, suggest TWO strategies individuals can use to reduce the amount of carbon dioxide in the atmosphere.
Reduce carbon emissions: One strategy is to reduce personal carbon emissions by conserving energy and using renewable energy sources. For example, individuals can use energy-efficient appliances, turn off lights
Plant trees and support reforestation efforts: to plant trees and support reforestation efforts, which can help to absorb and store carbon from the atmosphere.
Name ONE type of organism responsible for decomposing organic waste.
Bacteria
Explain how any TWO features of the human lung make it an efficient respiratory surface.
The human lung is an efficient respiratory surface due to its large surface area and thin walls.
The alveoli provide a large surface area for gas exchange, while the thin walls allow for rapid diffusion of gases across the membrane.
Explain how exercise may affect a person’s breathing rate.
During exercise, the body’s demand for oxygen increases as the muscles require more energy to work. In response, the breathing rate increases to deliver more oxygen to the lungs and remove excess carbon dioxide from the body.
Explain how smoking may affect a person’s breathing rate.
The chemicals in tobacco smoke can irritate and damage the airways, which can lead to inflammation and narrowing of the air passages. This makes it harder for air to flow in and out of the lungs, which can result in shortness of breath and decreased lung function.
Describe TWO events that occur in EACH of the following stages of meiosis I.
Prophase I
During Prophase I of meiosis I, homologous chromosomes pair up to form tetrads, and crossing-over occurs, leading to the exchange of genetic material between the homologous chromosomes, which increases genetic diversity.
Describe TWO events that occur in EACH of the following stages of meiosis I.
Anaphase I
During Anaphase I of meiosis I,
homologous chromosomes separate and are pulled to opposite poles of the cell, facilitated by spindle fibers.
Anaphase I also marks the completion of reduction division, reducing the number of chromosomes in each daughter cell by half.
Describe TWO events that occur in EACH of the following stages of meiosis I.
Telophase I
During Telophase I of meiosis I
Nuclear membranes reform around each set of chromosomes, forming two haploid nuclei. Cytokinesis occurs, dividing the cell cytoplasm into two haploid daughter cells.
Mutation and sexual reproduction are two processes which can lead to variation in the population of a species. State ONE way in which both processes are similar and TWO ways in which they differ.
Similarity - they both introduce genetic variation in the population of a species.
Differences
Source of Variation - Mutation creates new genetic variation by changing the DNA sequence, while sexual reproduction shuffles and recombines existing genetic variation inherited from the parents.
Rate of variation - Mutation occurs at a relatively slow rate, while sexual reproduction can introduce variation more rapidly
Explain the difference between variation in a community and variation in a population
Difference
Variation in a community refers to the differences among the populations of different species that coexist in a given area or ecosystem. On the other hand, variation in a population refers to the differences among individuals of the same species that exist within a population.
