Seasons and Adaptations of Plants and Animals Chapter Notes | Year 5 Science IGCSE (Cambridge) - Class 5 PDF Download

Earth's Orbit Around the Sun

Seasonal Orbits

• The Earth travels around the sun in a path known as an orbit, while also spinning on its axis.
• This orbit is slightly elliptical, resembling an egg shape, but it is not a perfect ellipse.
• Due to this elliptical shape, the distance between the Earth and the sun varies, averaging about 150 million kilometers.
• The Earth moves in an anticlockwise direction around the sun.
• It takes approximately 365.25 days, or one year, for the Earth to complete one full orbit, covering a distance of about 940 million kilometers.
• The sun's immense size creates a strong gravitational force that keeps the Earth in its orbit.

Understanding the Earth’s orbit around the sun is crucial for explaining the changing seasons.

The Seasons

• The seasons— spring, summer, autumn, and winter —are a result of the Earth’s orbit around the sun and the tilt of its axis.
• Each season corresponds to a specific position of the Earth in its orbit around the sun.
• The timing of the seasons differs between the northern and southern hemispheres:
• In the northern hemisphere, which includes countries between the Equator and the North Pole, when it is summer, the southern hemisphere, which includes countries between the Equator and the South Pole, experiences winter, and vice versa.
• The tilt of the Earth’s axis is responsible for these seasonal variations:
• In June, the northern hemisphere is tilted toward the sun, receiving more daylight and enjoying summer, while the southern hemisphere is tilted away from the sun, experiencing winter.
• In March and September, the Earth’s axis is positioned so that both hemispheres receive equal daylight, resulting in spring or autumn.
• At the Equator, there are no distinct seasons, as day and night are of equal length throughout the year.

The tilt of the Earth and its orbit around the Sun create varying seasonal effects across the globe.

Seasonal Shifts

Seasonal Changes: Sunrise and Sunset Times

• The times when the sun rises and sets change throughout the year because of how the Earth is tilted and how it moves around the Sun.
• This change affects how long the day lasts.
• To find out the length of the day, we subtract the time the sun rises from the time it sets.
• Days are longer in the summer and shorter in the winter.

How Plants Are Adapted to the Seasons

• Plants change with the seasons, especially in places where autumn and winter are clear.
• Leaves have a green pigment called chlorophyll that helps make food through photosynthesis.
• In autumn, when days get shorter and there is less sunlight, chlorophyll breaks down.
• This causes the leaves to change colour to yellow, red, and brown before they fall off.
• During winter, trees go into a dormant state, which means they stop growing and lose their leaves to save energy.
• In spring, when it gets warmer, new leaves start to grow.
• By summer, trees are covered in green leaves again.

Hibernation

Desert Survival

• Hibernation is a state of deep sleep during which an animal's heart rate, breathing, and body temperature drop significantly.
• Before entering hibernation, animals such as bears consume large amounts of food to build up fat reserves.
• Other animals, like mice, store food such as nuts and seeds in preparation for hibernation.
• Hibernation typically occurs during autumn and winter, with animals waking up in spring when conditions become more favorable.

Migration

• Migration is the process by which animals travel long distances to warmer areas with more abundant food when local resources are scarce.
• For instance, wildebeest in central Africa migrate approximately 3,000 kilometers each year in search of new grass, following seasonal rains.
• Birds, such as Siberian cranes, migrate from Russia and northern Europe to India at the end of summer in search of food.
• Grey whales undertake a migration of 8,000 kilometers from the Bering Sea to the lagoons of Baja California, Mexico, where they feed in the summer and breed in the winter.
• Prior to migration, animals often increase their food intake to build up energy reserves for the long journey.

Adaptations in Hot, Dry Environments

• Adaptations refer to the specific features that enable plants and animals to survive in their particular environments.
• Deserts are characterized by limited water resources, with infrequent rainfall that evaporates rapidly due to the intense heat.
• Plants and animals in desert environments have evolved to conserve water and withstand extreme conditions.

Cactus Plants

• Cactus plants have developed several adaptations to thrive in hot, dry environments:
• Thorns or spines replace leaves, reducing water loss through transpiration.
• A waxy coating on the stem helps prevent water evaporation.
• Fat-storing stems allow cacti to store water for extended periods.
• Deep roots enable cacti to reach underground water sources that are scarce.

Camels

• Camels possess unique adaptations that allow them to survive in harsh desert conditions:
• They can go for weeks without water and several months without food.
• Their humps store fat, which provides energy during food shortages.
• Long eyelashes protect their eyes from sand and debris.
• Wide, tough feet enable camels to walk on hot sand without discomfort.
• Thick lips allow them to eat thorny desert plants that other animals cannot.

Smaller Desert Animals

• Smaller animals such as rats and lizards have their own adaptations for surviving in hot, dry environments:
• They dig burrows to escape the heat during the hottest parts of the day.
• They are often nocturnal, being active at night when temperatures are cooler.

Adaptations of Plants and Animals in Different Environments

Frosty Flora

Organisms are adapted to live in their surroundings. An organism’s habitat is the place where it lives. The habitat provides the organism with all the resources it needs to survive and reproduce.

Adaptations of Plants and Animals in Wet Environments

• Wet environments, such as rivers, lakes, and seas, are rich in water, and both plants and animals have evolved specific adaptations to thrive in these areas.
• For instance, water lilies and lotus plants possess large, flat leaves that float on the water's surface, allowing them to capture maximum sunlight.
• The buoyancy of water supports their weak stems, eliminating the need for strong structural support.
• These plants have small roots because they are constantly submerged in water and do not require deep anchorage.
• Fish are equipped with gills that extract oxygen from water, enabling them to breathe.
• Fins facilitate efficient swimming.
• Water birds, such as ducks and geese, have webbed feet that function like flippers, making swimming easier.
• Seabirds possess waterproof feathers that allow them to dive for food without becoming soaked.
• They also have specialized glands that remove excess salt from the seawater they consume.
• Flamingos have long, slender legs that enable them to wade in shallow water.
• Their long, flexible necks allow them to reach food beneath the water's surface.

Adaptations of Plants and Animals in Cold Environments

• Cold environments, such as those near the North and South Poles, experience long, dark winters, minimal rainfall, and abundant snow, with only the top few centimetres of soil thawing during the brief summer.
• For example, fir trees have shallow roots that grow in the thawed surface soil during summer, avoiding the frozen layers beneath.
• The needles of fir trees have a waxy coating that reduces water loss.
• Sloping branches help snow slide off, preventing branch breakage.
• Thick bark and resin insulate the tree, retaining warmth and keeping moisture out.
• Animals like bears and moose have thick fur that provides insulation against freezing temperatures.
• Some animals enter hibernation during cold periods or when food is scarce, conserving energy.
• Others migrate to warmer regions in search of food during harsh winter months.

Adaptations of Predators and Prey

• Predators possess various adaptations that aid them in hunting and capturing their prey effectively.
• These adaptations may include sharp teeth, acute senses, and swift reflexes.
• Conversely, prey animals often develop traits to escape or avoid being caught, such as speed, camouflage, and protective behaviours.

Predators

Survival Tactics

• Predators possess distinct characteristics that enhance their hunting abilities, making them proficient at capturing prey.
• For instance, cheetahs can reach speeds of up to 112 km/h, which is more than four times faster than humans, due to their streamlined body structure.
• Predators like cheetahs have forward-facing eyes, which aid in accurate distance perception.
• Camouflage assists certain species, such as grasshoppers and specific deer, in blending into dry grass, facilitating a stealthy approach to prey.

General Predator Adaptations

• Speed for pursuing prey.
• Streamlined body shape for efficient movement.
• Camouflage to remain unseen by prey.
• Venom for immobilizing or killing prey, as seen in cobras and scorpions.
• Trapping techniques, like spider webs.
• Exceptional eyesight, as demonstrated by eagles, which can detect prey from 3 km away.
• Acute sense of smell, like dogs and bears, capable of scenting prey from a distance.
• Sharp and strong teeth and claws for capturing and killing.
• Cooperative hunting, as observed in African wild dogs that hunt in packs.
• Enhanced hearing to locate prey.

• Chameleons use camouflage and a fast, extendable tongue to catch beetles.
• Snakes, like cobras, can spit or inject venom to subdue their prey.
• Eagles have sharp talons for gripping their catch.
• Crocodiles rely on stealth and powerful jaws to catch prey in water.

Adaptations of Prey

• Prey animals possess specific adaptations to help them evade predators, employing various defence or attack strategies.
• For example, springboks live in large groups for protection, decreasing the likelihood of being isolated.

Defence Strategies

• Hiding through camouflage, like moths and fish that merge into their environment.
• Forming groups, such as zebras and wildebeest, with some animals serving as lookout.
• Bees utilize group defence, with guard bees alerting danger to safeguard the hive.
• Possessing physical features, like the hard shells of tortoises and turtles that they can retreat into when threatened.
• Sideways vision in lizards, antelopes, and fish, enabling them to detect predators from various angles.
• Speed for fleeing, as demonstrated by antelopes outrunning lions or cheetahs.
• Octopuses can expel ink clouds to bewilder predators and swim away swiftly.

Attack Strategies

• Weapons such as stings from bees and wasps.
• Acid sprays from certain ants.
• Horns of rhinos, antelopes, gemsbok, and buffalo.
• Quills from porcupines to deter or injure predators.
• Porcupines can shake their quills to seem intimidating and may charge backward to stab predators.