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Why Dinosaurs became extinct? Why Dinosaurs became extinct? The last dinosaurs died approximately 65 million years ago. Dinosaur extinction theories have been the subject of much debate and controversy. A recent explanation, supported by many scientists, suggests that a big meteorite crashed into Earth, changing the climatic conditions so dramatically that dinosaurs could not survive, ash and gas spewing from volcanoes suffocated many of the dinosaurs, diseases wiped out entire populations of dinosaurs, food chain imbalances lead to the starvation of the dinosaurs. Now we'll introduce just a few of the popular theories dealing with the extinction of species and evolution of species. Come let's explore evolution– the most exciting era.

Learning Objectives

After completing the topic, the student will be able to:

  • Define and discuss the complexity of “life”.
  • Define and describe the terms – evolution, homeostasis, metabolism, growth, adaptation, and reproduction.
  • Discover how life evolved.
  • Explore Darwin's theory of evolution and examine how natural selection leads to adaptation.
  • Define and discuss the term variations and analyze how they are evolved.
  • Define and discuss the terms – Homeostasis, metabolism, growth and reproduction in living organisms.
  • Explore how living things tend to change according to the environment.
  • Examine the life's dual nature of unity and diversity.
What is life Biology is the science concerned with the study of life Life is a condition that distinguishes living things (animals and plants) from inorganic matter (dead & decaying), in many aspects like growth, reproduction and other functional activities etc.
Exploring Life - What is Living?

There is no universal definition of life; there are a variety of definitions proposed by different scientists. To define life in unequivocal terms is still a challenge for scientists.

Life is a condition that distinguishes organisms from inorganic matter, which is manifested by growth through metabolism, reproduction and the power of adaptation to environment through changes originating internally.

According to physicists such as Erwin Scrodinger, life feeds on negative entropy by decreasing the internal entropy of organisms at the expense of free energy taken in from the environment and subsequently rejected in a degraded form.

Properties common to a diverse array of living organisms such as plants, animals, fungi, protists, archea and bacteria include a cellular structure with heritable information. They undergo metabolism, possess a capacity to grow, respond to stimuli, reproduce and through natural selection adapt to their environment in successive generations. So life is defined by scientists as a characteristic of organisms that exhibit the phenomena.

Panting dog Dogs regulate their body temperature through panting. Have you ever wondered why dog pants on hot days? It's because dog tries to maintain homeostasis. Homeostasis is a word that biologists use to describe how a living organism regulates its internal environment to maintain stability. One very important part of homeostasis is body temperature.
Homeostasis

Homeostasis is the property of any system especially a living organism, that regulates its internal environment so as to maintain a stable, constant condition. It is the tendency or ability of an organism or a cell to maintain internal equilibrium by adjusting its physiological processes. Body temperature in mammals, for example, is regulated by a sensor that contains the cells within the hypothalamus of the brain, sweating to reduce temperature.

Other homeostatic mechanisms include: those controlling blood glucose levels, blood acidity, and hormone secretions. It was also suggested that percentage fat composition and body weight have similar control systems. These homeostatic mechanisms involve the neural and endocrine systems of mammals.

Organization: Every organism has a definite biological organization. The external appearance of organism is invariably accompanied by an even more complex internal structure. Plants as well as animals are composed of a number of elements. Atoms in the body of an organism are again united into simple and complex molecules, which are further arranged to form different units like cells, tissues, organs.