What are plants

Plants

Plants are multicellular eukaryotic autotroph organisms that can reproduce through Vegetative reproduction, Asexual reproduction and sexual reproduction.

What is ZOOLOGY

                                                             Zoology

Zoology(Gr. zoon , logos, to study) is the study of animals. It is one of the broadest fields in all of science because of the immense variety of animals and the complexity of the processes occurring within animals. There are, for example, over 20,000 described species of bony fishes and over 300,000 described (and many more un described ) species of beetles! It is no wonder that zoologists usually specialize in one or more of the sub disciplines of zoology. They may study  particular  functional,  structural,  or  ecological  aspects  of  one  or  more  animal  groups (table 1.1), or they may choose to specialize in a particular group of animals (table 1.2). Ichthyology,  for  example,  is  the  study  of  fishes,  and  ichthyologists  work  to understand the structure, function, ecology, and evolution of fishes. These studies have uncovered an amazing diversity of fishes. One large group, the cichlids, is found in Africa (1,000 species), Central and South America (300 species), India (3 species) and North America (1 species). Members of this group have an enormous variety of color patterns (figure  1.1),  habitats,  and  body  forms.  Ichthyologists  have  described  a  wide  variety  of feeding habits in cichlids. These fish include algae scrapers, like Eretmodu , that nip algae with chisel-like teeth; insect pickers, like Tang anicodus; and scale eaters, like Perissodus. All cichlids have two pairs of jaws. The mouth jaws are used for scraping or nipping food, and the throat jaws are used for crushing or macerating food before it is swallowed .Many cichlids mouth brood their young. A female takes eggs into her mouth after the eggs are spawned. She then inhales sperm released by the male, and fertilization and development take place within the female’s mouth! Even after the eggs hatch, young are taken back into the mouth of the female if danger threatens (figure 1.2). Hundreds of variations in color pattern, body form, and behavior in this family of fishes illustrate the remarkable diversity present in one relatively small branch of the animal kingdom. Zoologists are working around the world to understand and preserve the enormous diversity.

Reference:

Miller−Harley: Zoology, Fifth Edition.

What the science Basically is?

                                                                      SCIENCE

Science is a methodical approach to studying the natural world. Science asks basic questions, such as how does the world work? How did the world come to be? What was the world like in the past, what is it like now, and what will it be like in the future? These questions are answered using observation, testing, and interpretation through logic.

Reference:

Why most cells are small

WHY ARE MOST CELLS SMALL?

Most cells are small and can be seen only with the aid of a microscope.  (Exceptions include the eggs  of  most  vertebrates  [fishes, amphibians, reptiles, and birds] and some long nerve cells.) One reason for the smallness of cells is that the ratio of the volume of the cell’s nucleus to the volume of its cytoplasm must not be so small that the nucleus, the cell’s major control center, cannot control the cytoplasm. Another aspect of cell volume works to limit cell size. As the radius of a cell lengthens, cell volume increases more rapidly than cell surface area (figure 2.3). The need for nutrients and the rate of waste production are proportional to cell volume. The cell takes up nutrients and eliminates wastes through its surface plasma membrane. If cell volume becomes too large, the surface area-to-volume ratio is too small for an adequate exchange of nutrients and wastes.

Summary of development of frog

Summary of development of frog:

 

1-      Egg + zygote = fertilization

2-      Zygote = rapid division of cells

3-      Meurola= formation of blastocells

4-      Blastolla= gestrolation

5-      Gestrolla= elongation of embryo and formation of neural tubes 

6-      Neurolla= development of tails and gills

7-      Tadepol= metamorphosis -->  adult frog

 

The Hardy- Weinberg theorem of population:

The Hardy- Weinberg theorem:

In 1908, English mathematician Godfrey H. Hardy and German physician Wilhelm Weinberg independently derived a mathematical model describing what happens to the relative frequency of alleles in a sexually reproducing population over time. Their combined ideas became known as the Hardy-Weinberg Theorem. It states that the mixing of alleles at meiosis and their subsequent recombination do not alter the relative frequencies of the alleles in future generations, if certain assumptions  are met. Stated another way, if certain assumptions are  met, evolution will not occur because the relative allelic frequencies will not change from generation to generation, even though the specific mixes of alleles in individuals may vary.

The assumptions of he Theorem are:

1-      Population size must be large. Large size ensures that gene frequency will not change by chance alone.

2-      Individuals cannot migrate into or out of the population. Migration may introduce new alleles into the gene pool or add or delete copies of existing alleles.

3-      Mutations must not occur. If they do, mutational equilibrium must exist. Mutational equilibrium exists when mutation from the wild type allel to a mutant forn is balanced by the mutation from the mutant form back to the wild type. In either case, no new genes are introduced into the population from the sources.

4-      Sexual reproduction within the population must be random. Every individuals must have and equal chance of mating with any other individuals in the population. If this condition is not fulfilled then some individuals are more likely too reproduced than others, and natural selection may occur.

These assumptions must be met if allelic frequencies are not changing that is if evolution is not occurring. Clearly, these assumptions are restrictive and few, if any real population meet them. This mean that most population are evolving.The Hard-Weinberg Theorem does provide a useful theoretical frame work for examining changes in allelic frequencies in population.

CONCEPT OF EVOLUTION

CONCEPT OF EVOLUTION

Main aspects for assignment on concept of evolution are

→ Theories of evolution

→ Homologue and analogue

→ Evidances of evolution

→ Hardy Weinberg Theorm

→ Fossil and fossilization

→Types of frog and their geological scale

°THEORIES OF EVOLUTIONt:

“The formation of complex organisms from simple one ,with the passage of time is known as the process of evolution”

Many scientists made many hypothesis for the concept of evolution,some historical aspects about evolution are given below

1-ARISTOTLE (322-384)B.C

He described concepts of change in living organisms over time.

2-Georges-Louis Buffon(1707-1788)

He spent many years studying comparative anatomy. His observations of structural variations in particular organs of related animals convinced him that change must have occurred during the history of life on earth. Buffon attributed change in organisms to the action of the environment. He believed in a special creation of species and considered change as being degenerate. For example, he described apes as degenerate humans.

3-Eramus Darwin(1731-1802)

A Physician and the grandfather of Charles Darwin, was intensely interested in questions of origin and change. He believed in the common ancestry of all organisms.

4- Jean Baptiste Lamarck (1744-1892)       

He was a distinguished French zoologist. His contributions to zoology include important studies of animal classification. Lamarck published a set of invertebrate zoology books. His theory was based on a widely accepted theory of inheritance that organisms develop new organs, or modify existing organs. Lamarck believed that “ need “ was dictated by environmental change and that change involved movement toward perfection. The idea that change in a species is directed by need logically led Lamarck to the conclusion that species could not become extinct, they simply  evolved into different species.

Lamarck illustrated his ideas of change with the often-quoted example of giraffe. He contended that ancestral giraffes had short necks, much like those of any other mammal. Straining to reach higher branches during browsing resulted in their acquiring higher shoulders and longer necks. These modifications, produced in one generation, were passed on to the next generation. Lamarck published his theory in 1802 and included it in one of his invertebrate zoology books, Philosophie Zoo (1809). He defended his ideas in spite of intense social criticism.

Lamarck’s acceptance of a theory of inheritance that we now know is not correct led him to erroneous conclusions about how evolution occurs. There is no evidence that changes in the environment can initiate changes in organisms that can be passed on to future generations. Instead, change originates in the process of gamete formation.

Homology and Analogy:

Structures and processes of organisms may be alike. There are two reasons for similarities, and both cases provide evidence of evolution. Resemblance may occur when two unrelated organisms adapt to similar conditions. For example, adaption for flight have produced flat, gliding surfaces in the wings of birds and insects. These similarities indicate that independent evolution in these two groups of animals to exploit a common aerial environment. The evolution of superficially similar structures in unrelated organisms is called convergent evolution, and the similar structures are said to be analogous.

Resemblances may also occur because two organisms share a common ancestry. Structures and processes in two kinds of organisms that are derived from common ancestry are said to be homologous. Homology can involve aspects of an organism’s structure, and these homologies are studied in the discipline called comparative anatomy. Homology can also involve aspects of animal development and function and homologous processes are studied using techniques of molecular biology.

Evidences of evolution:

Biogeography:

It was the geographical distribution of species---- biogeography---- that first suggested the idea of evolution to Darwin. Islands have many species of plants and neighboring island. Consider armadillos, the armored mammals that live only in America. The evolutionary view of biogeography predicts that contemporary armadillos record confirms that such ancestors existed.

The Fossil Record:

The succession of fossil forms is a strong evidences in favour of evolution. It provides a visual record in a complete series showing the evolution of an organism. For instance, evidence from biochemistry, molecular biology and cell biology places prokaryotes as the ancestors of all life and predicts and bacteria should precede all eukaryotic life in the fossil record. Indeed, the oldest known fossils are prokaryotes.

Comparative Anatomy:

Anatomical similarities between species grouped in the same taxonomic category bring another support  to the theory of the Descent with modification. For example, the same skeletal elements make up the forelimbs of human, cats, whales, bats, and all other mammals, although these appendages have very different functions. The basic similarity of these forelimbs is the consequence of the descent of all mammals from the common ancestor. The arms, wings, flippers, and forelegs of different mammals are variations on a common anatomical theme that has been modified for divergent functions. Similarities in characteristics resulting from common ancestry is known as homology, and such anatomical signs of evolution are called homologous structures. Common anatomy supports that evolution is a remodeling process in which ancestral structures that functioned in one capacity become modified as they take on new functions. The flower parts of a flowering plant are homologous. They are considered to have evolved from leaves to form sepals, petals, stamens and carpels.

The oldest homologous structures are vestigial organs, rudimentary structures of marginal, if any use to the organism. Vestigial organs are historical remnants of structures that had important functions in ancestors but are no longer essential presently.

Comparative Embroyology:

Closely related organisms go through similar stages in their embryonic development. For example, all vertebrate embryos go through a stage in which they have gill pouches on the slides of their throats. At embryonic stage of development, similarities between fishes, frogs, snakes, birds, humans, and all other vertebrates are much more apparent than differences. As development progresses, the various vertebrates diverge more and more, taking on the distinctive characteristics of their classes.

Molecular biology:

Evolutionary relationships among species are reflected in their DNA and proteins--- in their genes and gene products. If two species have genes and copied from a common ancestor. For example, a common genetic code brings evidence that all life is related. Molecular biology thus provided strong evidence in support of evolution as the basis for the unity and diversity of life.

References: 

                        Stephen A. Miller and John P. Harley 8th edition