Responsiveness is the ability of an organism to adjust to changes in its internal and external environments.

A change in an organism’s surroundings that causes the organism to react is called a stimulus (plural stimuli).

Homeostasis is the ability to maintain a relatively stable internal state that persists despite changes in the world outside. All living organisms, from plants to puppies to people, must regulate their internal environment to process energy and ultimately survive.

1. Adaptation is the evolutionary process whereby an organism becomes better able to live in its habitat or habitats. 2.

Animals need food, water, shelter, and space to survive. Herbivores can live only where plant food is available. Carnivores can live only where they can catch their food. Omnivores can live in many places because they eat both plants and animals.

(a) If the plants and animals disappear from the Earth’s surface, then the ecological balance will be disturbed. Without plants there will be no oxygen available for breathing after some time and everybody will die. These animal and plant species, including humans, are all interdependent.

As species disappear, infectious diseases rise in humans and throughout the animal kingdom, so extinctions directly affect our health and chances for survival as a species. The rise in diseases and other pathogens seems to occur when so-called “buffer” species disappear.

The earliest known life-forms are putative fossilized microorganisms, found in hydrothermal vent precipitates, that may have lived as early as 4.28 Gya (billion years ago), relatively soon after the oceans formed 4.41 Gya, and not long after the formation of the Earth 4.54 Gya.

Far bigger than any dinosaur, the blue whale is the largest known animal to have ever lived. An adult blue whale can grow to a massive 30m long and weigh more than 180,000kg – that’s about the same as 40 elephants, 30 Tyrannosaurus Rex or 2,670 average-sized men.