NCERT Based Activity: Our Home: Earth, a Unique Life Sustaining Planet

Activity 13.1: Let us find out

List some features of the Earth that we often take for granted, but are interesting and important to us. Write them in Table 13.1. We have filled in a few for you.

Ans:

• Sunlight and warmth from the Sun - these provide the energy needed for photosynthesis in plants and keep the global temperature within a range that supports life.
• Water in all three forms - solid (ice), liquid (water) and gas (water vapour). This allows the continuous movement of water through the water cycle and supports all forms of life.
• An atmosphere - a mixture of gases (mainly nitrogen and oxygen) that supplies air for breathing, helps regulate temperature, and protects organisms from harmful solar radiation.
• A protective ozone layer - a layer in the upper atmosphere that absorbs most of the Sun's harmful ultraviolet (UV) radiation, reducing damage to living tissues.
• A magnetic field - generated by the motion of liquid iron in the core; it shields the Earth from charged particles of the solar wind and helps retain the atmosphere.
• Suitable distance from the Sun (the Goldilocks zone) - the Earth is at a distance where temperatures allow liquid water to exist on the surface.
• Gravity - keeps the atmosphere and oceans bound to the planet and allows structures such as mountains and rivers to form and persist.
• Rotation and revolution - rotation of the Earth causes day and night; revolution around the Sun together with the axial tilt causes the seasons.
• The axial tilt and the Moon's stabilising effect - the tilt of the Earth's axis produces seasonal changes; the Moon helps keep this tilt relatively stable over long timescales.
• Diverse spheres and habitats - the lithosphere (land), hydrosphere (water), atmosphere (air) and biosphere (living organisms) interact to create many different habitats supporting biodiversity.
• Plate tectonics and recycling of materials - movement of Earth's plates causes earthquakes and volcanoes, forms mountains and recycles minerals and gases essential for life.
• Availability of essential elements - elements such as carbon, hydrogen, oxygen, nitrogen and phosphorus occur in usable forms and participate in biological cycles.

Activity 13.2: Let us find out

• Collect information about the temperature and size of the planets in the Solar System, and check if they have an atmosphere.
• You may collect this information from books in your school library, trusted websites, or discuss with your teachers.
• Fill out the missing information in Table 13.2.

Ans:

Activity 13.3: Let us find out

• Take some parts of plants such as a stem cutting of a money plant, the 'eyes' of a sprouted potato, or a piece of ginger.
• Plant each of them separately in moist soil (not too deep). For the money plant, you can also place a cutting in a glass container with water so that it is easy to observe root formation.
• Ensure proper conditions - provide suitable water, air, and sunlight; avoid waterlogging; keep them at a stable temperature.
• Observe daily and note how many days it takes for roots, stems and leaves to appear; record when the first new leaf appears.

Observation:

• Roots may appear in about 3-7 days for money plant cuttings placed in water, and about 7-14 days for potato eyes or ginger placed in moist soil depending on temperature and moisture.
• Stems and leaves typically emerge within about 10-20 days after planting; the first new leaf often appears around 15-25 days, but this varies with plant type and environmental conditions (money plant in water often shows leaves sooner than tubers in soil).

Explanation and additional points to record

• Vegetative propagation - the process used here is a form of asexual reproduction where a new plant develops from a part of the parent plant (stem, tuber, rhizome). The new plant is genetically identical to the parent.
• Role of plant hormones - natural hormones such as auxins promote root formation at cut surfaces; availability of these hormones and their movement affect how quickly roots form.
• Why roots often form first - roots are essential for water and mineral uptake; when a cutting is placed in water or soil, cells near the cut differentiate into root initials under the influence of hormones and moisture.
• Factors affecting growth - temperature, light intensity, humidity, the quality of the cutting or tuber, and the cleanliness of tools; warmer but not hot temperatures usually speed up rooting.
• Recording observations - maintain a simple table with columns: date, plant part, condition (water/soil), first root observed (date), first leaf observed (date), notes on health/colour/size. This helps compare species and conditions.
• Precautions - use clean pots and scissors to avoid infection; do not overwater; label each sample so you can track observations correctly.
• Conclusion/Application - this activity demonstrates how many common plants can reproduce asexually, and it shows conditions necessary for growth. Such techniques are used in gardening and agriculture to propagate desirable plants quickly and reliably.