Chapter 2: The Living State of Plants & Animals PDF

CHAPTER 2- The Living State of Plants and Animals A. What is Life? - “A life form is a matter form capable of undergoing Darwinian evolution; a living entity is a self-sustaining chemical system – in nature, it results from the Darwinian evolution and...

CHAPTER 2- The Living State of Plants and Animals A. What is Life? - “A life form is a matter form capable of undergoing Darwinian evolution; a living entity is a self-sustaining chemical system – in nature, it results from the Darwinian evolution and might engage into further Darwinian evolution”. ✓ Life is capable of METABOLISM - chemical reactions which utilize energy and also synthesize its cellular constituents. ✓ Life is capable of SELF-REPLICATION - they pass their traits from generation to generation and can produce offspring. ✓ Life can EVOLVE in order to adapt to environmental changes. ✓ Life is a community of organisms which must interact with their nonliving environment through processes called biogeochemical cycles. *Even very simple, single-celled organisms are remarkably complex: inside each cell, atoms make up molecules; these in turn make up cell organelles and other cellular inclusions. B. Characteristics of Life 1. Reproduction ✓ When reproduction occurs, genes containing DNA are passed along to an organism’s offspring. ✓ These genes ensure that the offspring will belong to the same species and will have similar characteristics, such as size and shape. 2. Growth and Development ✓ Organisms grow and develop following specific instructions coded for by their genes. ✓ These genes provide instructions that will direct cellular growth and development, ensuring that a species’ young will grow up to exhibit many of the same characteristics as its parents. 3. Regulation ✓ Even the smallest organisms are complex and require multiple regulatory mechanisms to coordinate internal functions, respond to stimuli, and cope with environmental stresses. ✓ Two examples of internal functions regulated in an organism are nutrient transport (plants) and blood flow (higher animals). 4. Homeostasis ✓ Organisms are able to maintain internal conditions within a narrow range almost constantly, despite environmental changes, through homeostasis (literally, “steady state”)—the ability of an organism to maintain constant internal conditions.  5. Energy Processing ✓ All organisms use a source of energy for their metabolic activities. ✓ Some organisms like plants capture energy from the sun and convert it into chemical energy in food (photosynthesis); others use chemical energy in molecules they take in as food (cellular respiration). C. Theories on the Origin of Life 1. SPONTANEOUS GENERATION/ABIOGENESIS - is an archaic scientific theory which stated that living organisms could arise from nonliving matter and that such a process was regular in nature. Examples are: 1. a piece of bread and cheese wrapped in rags and left in a dark corner could give rise to mice in a few weeks; 2. Many also believed this theory due to the occurrences of maggots on decaying meat. 2. BIOGENESIS - “Life from pre-existing life” - The theory states that new living organisms can only emerge from other previously existing living organisms - This concept is considered fact to date, which explains how each form of life reproduces its own kind. 3. PANSPERMIA/COSMOZOIC/INTERPLANETARY - This theory state that life on earth began as spores or cosmozoa originating from other planets or solar system. - 4. SPECIAL CREATION - As stated in the Book of Genesis this theory claims that a Creator made all the living organisms. 5. BIOCHEMICAL EVOLUTION OF LIFE THEORY - The currently accepted theory on the origin of life which is backed up by a set of evidences tested in a laboratory condition particularly on chemical evolution. - The presence of DNA in chloroplasts and mitochondria, aggregations of cells, and fossils are evidences supporting this theory. - The evolution of life occurred when Earth was still young, and these changes were results from the earth’s condition at the time, and through time. D. Differences of Plants and Animals Basis of Comparison Plants Animals  Animals are the living Plants are green in color organisms which feed on due to the presence of the the organic material and chlorophyll and are able to are known to have a prepare their own food specialized system in 1. Meaning with the help of sunlight, their body like the nervous water and carbon dioxide. system, reproductive They are known for system, sense organs, providing oxygen to the which make them unique atmosphere. from the other forms of life. Plants do not have the ability to move from one Animals can move from place to another, as plants one place to another 2. movement are rooted into the ground, freely, and exceptions are exceptions are Volvox and Sponges and Corals. Chlamydomonas. Plants have chlorophyll, Animals are the due to which they have the heterotrophs, as they 3. Mode of Nutrition capability to prepare their depend on plants for their own food and are known food, either directly or as autotrophs. indirectly. Animals have the proper Plants do not have the digestive system which digestive system, and the support the food in 4. Storage of Food storage of food digesting and absorbing (carbohydrate) takes nutrition from it, the food place in the form of starch. (carbohydrate) is stored in the form of glycogen. Plants take in carbon Animals take in oxygen dioxide and release and release carbon oxygen into the dioxide into the 5. Respiration atmosphere, exchange of atmosphere, which gases occurs through occurs through lungs, stomata. gills, skin, etc. The cellular structure of The cellular structure of plants contains the cell animals does not have wall, chloroplast, 6. Cellular Structure cell walls, though other plasmodesmata, plastids organelles like the tight and other different junction, cilia are present. organelles. The growth of the plants takes place throughout the The organs and organ life, the meristematic 7. Growth system supports the system present in the tip of growth and is definite. roots and stems supports the growth. Reproduction of plants Some lower animals like 8. Reproduction takes place asexually like algae reproduce by budding, vegetative asexually while higher  methods, spores, wind, or animals reproduce through insects. sexually. They have proper Plants show the response nervous system and to stimuli like touch, light, response to any stimuli in 9. Response though are less sensitive a fraction of seconds, so due to the absence of the they are regarded as sense organs. highly sensitive.