species and their environment 

The City School: Science Notes

Worksheet Number: Science 2.8.5

Topic: Species and Their Environment

  • Asteroids
      - Definition: Small rocky objects that did not form into planets or moons from the disc of dust and gases around the Sun.
      - Location of Asteroids:
        - Most asteroids are located in a ring known as the asteroid belt, situated between the orbits of Mars and Jupiter.
        - Two additional groups of asteroids, known as trojans, are found on either side of Jupiter and move in its orbit around the Sun.
        - Visual representation: Positions of the asteroid belt and trojans illustrated in Figure.

  • Asteroid Collision
      - Asteroids maintain their positions due to gravitational forces among themselves and with Jupiter.
      - Changes in gravitational forces can redirect an asteroid's path, potentially leading it to cross the orbits of planets.
      - Impact Craters:
        - When an asteroid collides with a planet or moon, it results in the formation of an impact crater.
        - Example: The Moon retains impact craters due to the absence of atmosphere, which prevents weathering and erosion.
        - Near Side vs. Far Side of the Moon:
          - Near Side: The side that faces toward Earth.
          - Far Side: The side that remains unseen from Earth.

  • Climate Change
      - Climate is influenced by the amount of sunlight and heat received from the Sun.
      - When an asteroid impacts Earth, it ejects dust and ash into the atmosphere, leading to the following effects:
        - If the impact occurs on land: Dust and ash block sunlight.
        - If the impact occurs in the sea: Water vapor and droplets obstruct sunlight.
        - Consequent effects: Darkened skies and cooling planet temperatures, sometimes referred to as impact winter.
        - Duration of impact winter: Can persist for several years.

  • Mass Extinction
      - Definition: An event where over 75% of plant and animal species become extinct.
      - Causes of extinction:
        - Shift in environmental conditions.
        - Various sources:
          - Volcanic eruptions emitting ash and smoke.
          - Variability in Earth's axial tilt leading to reduced heat in the northern hemisphere and the onset of ice ages.
      - Historical context: There have been five mass extinctions recorded in Earth's history.
        - The latest occurred approximately 66 million years ago and is linked to an impact winter.
        - Cretaceous-Paleogene Extinction:
          - Causes: Believed to be triggered by an asteroid impact.
          - Characteristics of the asteroid: Ranged between 11 and 81 kilometers in diameter, creating the Chicxulub crater (20 kilometers deep in Mexico).
          - Consequences: Instant firestorms, vast devastation, followed by an impact winter.

Date: 10th February 2026

Topic: Variations & Cell Division

  • Causes of Variations:
      - Between Different Species: Variations result from entirely different sets of genes, leading to diverse plans for growth and function.
      - Among Individuals Within a Species: Caused by genetic differences inherited from parents and influenced by environmental factors.

  • Human Blood Groups:
      - Type of Variation: Genetic variation.
      - Explanation: Blood groups are inherited from parents and remain constant throughout an individual's life.

Date: 11th February 2026

Topic: Theory of Natural Selection

  • Population Dynamics:
      - Despite continuous reproduction, the total number of individuals in a species remains stable.
      - Reason: Genetic variation influences survival; individuals whose characteristics are ill-suited to the environment do not survive (“survival of the fittest”).

  • Variation vs. Adaptation:
      - Variation: Differences among individuals of the same species.
      - Adaptation: Characteristics that enhance an organism's ability to survive in its environment.

  • Impact of Environmental Change on Characteristics:
      1. Variations exist within a population.
      2. Individuals with traits best suited to the environment survive, while lesser-adapted individuals die off.
      3. Successful individuals pass on advantageous genes to offspring.
      4. Over time, this may lead to the emergence of new species.

  • Adaptation to Environmental Changes:
      - Environmental changes lead to shifts in population traits due to natural selection.

Activity Question:

  • Scenario Inquiry:
      - Hypothesis: If climate change accelerates beyond the capacity of animals to adapt, the result could be catastrophic for species and create imbalances in food chains.
        - Explanation: Inability to adapt may lead to extinction, causing consumer food sources to collapse and resulting in population surges in species that typically are kept in check.

Date: 12th February 2026

Topic: Variation in Humans

  • Environmental Influence on Characteristics: The environment can modify various traits, including factors such as light exposure and nutritional availability.

  • Genetic vs. Environmental Traits:
      - Genetic Characteristics: Determined by genes (e.g., naturally blue eyes, curly hair).
      - Environmental Characteristics: Influenced by external factors (e.g., ability to speak French, presence of a scar).

  • Types of Variation:
      - Continuous Variation:
        - Examples: Height, weight, arm span.
      - Discontinuous Variation:
        - Examples: Blood group, handedness, eye color, ability to roll the tongue.

Date: 17th February 2026

Topic: Population & Extinction

  • Definition of Extinction:
      - Extinction occurs when no individuals of a species remain.
      - Causes of Extinction:
        - Invasive species, climate change, diseases, habitat destruction.

  • Impact of Invasive Species:
      - Invasive species disrupt the populations of native species by consuming their resources (e.g., tilapia fish depleting local fish food sources).

  • Human Contribution to Extinction:
      - Carbon emissions and pollutants lead to climate change, affecting habitats and species survival.
      - Human activities such as deforestation and habitat alteration significantly impact biodiversity.

Date: 18th February 2026

Topic: Coral Bleaching and Extinction

  • Coral Bleaching Scenario:
      - Rising ocean temperatures cause coral reefs to lose color and essential algae, leading to the plight of species reliant on these ecosystems.
      - Consequences:
        1. Species dependent on coral reefs for food and shelter may face starvations.
        2. Loss of coral reefs may dramatically reduce biodiversity.

Scenario: Deforestation and Orangutans

  • Impacts of Deforestation:
      - Large-scale tree removal for plantations threatens orangutans' habitat.
      - Consequence: Potential extinction of orangutans due to food shortages and unsuitable living conditions.

Scenario: Drought and Frog Populations

  • Effects of Drought:
      - Prolonged drought decreases frog populations as breeding habitats diminish.
      - Result: Long-term drought could lead to extinction of frog species unable to adapt to changing environments.

Final Scenario: Genetic Variation among Families

  • Comparison of Identical Twins and Siblings:
      - Identical twins possess the same genes, resulting in minimized variation.
      - Non-identical siblings exhibit greater variation due to differing genetic compositions inherited from parents.

Conclusion

  • This extensive mapping demonstrates the interconnectedness of species, their environments, climate change, and the mechanisms driving evolution and extinction. Understanding these relationships is crucial for the preservation of biodiversity and ecosystem health.