Heredity and Evolution
Complete the following diagram.
Evidences of Evolution
Ans:-
1. Morphological
2. Similarities in bones structure
3. Comparative embryology
4. Fossil record
2. Read the following statements and justify the same in your own words with the help of suitable examples.
A. Human evolution began approximately 7 crore years ago.
Ans:- Around 7 crore years ago, dinosaurs became extinct, marking a significant point in history when human evolution began. The process of human evolution can be traced back to ancestors resembling monkey-like animals, similar in appearance to modern lemurs. Over time, these ancestral species further evolved into ape-like animals. Some of these ape-like animals eventually gave rise to gibbons and orangutans, while others evolved into gorillas and chimpanzees. From these evolutionary paths emerged the first human-like animal known as Ramapithecus.
The following table provides a timeline of the evolutionary history of modern humans:
Year Evolution
15 million years ago Dryopithecus (ape-like) and Ramapithecus (man-like)
3 - 4 million years ago Man-like primates
2 million years ago Australopithecines, also known as Homo habilis, lived in East Africa
1.5 million years ago Homo erectus
1,000 - 40,000 years ago Neanderthal man
75,000 - 10,000 years ago Homo sapiens
B. Geographical and reproductive isolation of organisms gradually leads to speciation.
Ans:-Speciation can be defined as a process in evolution where one or more species emerge from an existing species. To illustrate the concept of speciation, let's consider the example of beetles. Imagine a population of beetles that has separated into two distinct groups unable to interbreed.
These two groups of beetles inhabit different areas within a wide mountain range, as their food sources are dispersed. Consequently, the beetle population in this region is quite large. Since beetles are small insects with limited mobility, they primarily gather food from nearby locations. This leads to the formation of sub-populations spread across the area, which can eventually give rise to entirely new species.
Geographical isolation plays a crucial role in speciation. Due to the large area over which the beetle population is distributed, reproduction between individuals from different sub-populations becomes unlikely. Instead, reproduction occurs within each sub-population, leading to the emergence of distinct species. If a river were to form between the two populations, it would further isolate the sub-populations, reducing the chances of gene flow or interbreeding.
Genetic drift and natural selection also contribute to speciation. Different sub-populations may undergo changes influenced by genetic drift or natural selection. For instance, a specific sub-population of beetles might evolve to have blue or green coloration due to these factors, leading to subsequent changes in future generations. Consequently, the two beetle populations become distinct from each other.
Eventually, the sub-populations become reproductively isolated, meaning they are unable to successfully interbreed. For instance, female beetles in one area might prefer to mate with males of the same coloration (e.g., green) due to the survival advantages associated with that color. As a result, a new species of green beetles forms, characterized by reproductive isolation.
It's important to note that the process of speciation is complex and can involve various factors, including geographic barriers, genetic changes, and reproductive isolation. The beetle example helps illustrate how these factors can contribute to the formation of new species over time.
C. Study of fossils is an important aspect of study of evolution.
Ans:- Fossils are remnants or traces of organisms that lived in the past and provide valuable evidence for understanding evolution. They offer insights into the characteristics of ancient organisms and the changes that have taken place over time, leading to the present diversity of life on Earth. Fossils preserve the shape and structure of the original organism, although their color and texture can vary due to the minerals that form them.
The importance of fossils in the study of evolution can be summarized as follows:
(i) Fossils provide information about the types of organisms that inhabited the Earth in the past.
(ii) Fossils reveal the extent of changes that have occurred in organisms over time.
(iii) Fossils provide a time reference for the existence of particular organisms.
fossils play a vital role in our understanding of evolution. They inform us about the diversity of past life forms, track changes in organisms over time, and provide a chronological framework for the existence of different species. By studying fossils, scientists can piece together the story of life on Earth and gain insights into the processes that have shaped the natural world.
D. There is evidence of fatal science among chordates.
Ans:-Fetal science, also known as embryology, provides evidence of evolution through the comparative study of embryos in vertebrates or chordates. The study of embryos reveals that there are significant similarities among them during the early stages of development, indicating a common origin of these organisms. As development progresses, the similarities gradually decrease, reflecting the divergence and adaptation of different species over time.
For example, if we compare the embryos of various vertebrates such as fish, reptiles, birds, and mammals, we can observe striking similarities in their early developmental stages. These similarities include the presence of a notochord, gill slits, and similar body segments. These shared characteristics suggest that these organisms share a common ancestry and have evolved from a common ancestor.
Q3. Complete the statements by choosing correct options from bracket.
(Gene, Mutation, Translocation, Transcription, Gradual development, Appendix)
A. The causality behind the sudden changes was understood due to Mutation principle of Hugo de Vries.
B. The proof for the fact that protein synthesis occurs through Gene was given by George Beadle and Edward Tatum.
C. Transfer of information from molecule of DNA to mRNA is called as Transcription process.
D. Evolution means Gradual development.
E. Vestigial organ Appendix present in human body is proof of evolution.
Q4. Write short notes based upon the information known to you.
A. Lamarckism
Ans:-Lamarckism, proposed by Jean-Baptiste Lamarck, is a theory of evolution that suggests that morphological changes in living organisms are responsible for evolution. Lamarck believed that these changes are caused by the activities or disuse of organs in an organism. He proposed the concept of "use or disuse of organs," stating that organisms develop certain characteristics through their actions or the lack thereof. Lamarck used examples such as the long neck of a giraffe, strong shoulders of an ironsmith, weak wings of flightless birds, and the loss of legs in snakes to support his theory.
B. Darwin’s theory of natural selection.
Ans:- Darwin's theory of natural selection, as presented in his book "Origin of Species," is a cornerstone in the field of evolutionary biology. Based on extensive observations of plants and animals, Darwin proposed the concept of survival of the fittest through natural selection.
Natural selection plays a crucial role in this process, as nature acts as the selector, favoring those organisms that are best adapted to their environment. The individuals that are less suited to their surroundings are less likely to survive and reproduce. Over time, this differential reproductive success results in the gradual evolution of species, as advantageous traits become more prevalent in populations.
While Darwin's theory of natural selection has been widely accepted, it has also faced certain objections. Some critics argue that natural selection is not the sole factor driving evolution, and other mechanisms, such as genetic drift and gene flow, also play significant roles. Additionally, there are debates regarding the distinction between useful and useless modifications, as well as the pace of evolutionary changes.
C. Embryology.
Ans:- Embryology is the study of the formation and development of embryos and foetuses. It provides evidence for evolution by showing similarities in early embryonic stages among different vertebrate species. These similarities suggest a common origin and shared evolutionary history. As development progresses, embryos diverge and develop species-specific characteristics. Comparative embryology supports the concept of common ancestry and helps in understanding the genetic changes that contribute to the diversity of life forms.
D. Evolution.
Ans:- Evolution is a gradual process of change that occurs in organisms over a long period of time. It is believed to have started around 3.5 billion years ago with the presence of simple elements on Earth, which eventually led to the formation of complex organic and inorganic molecules. Through further evolutionary changes, simple cells emerged, eventually giving rise to the wide variety of species we see today, ranging from unicellular organisms like Amoeba and Chlorella to complex organisms like humans and Banyan trees.
E. Connecting link.
Ans:- A connecting link is an organism that exhibits characteristics or traits that are intermediate between two distinct groups or lineages. These organisms serve as transitional forms, providing evidence for the evolutionary connection and common ancestry between different groups.
One example of a connecting link is Peripatus, also known as velvet worms. Peripatus exhibits characteristics that are shared by both annelids (segmented worms) and arthropods. It has a segmented body, similar to annelids, and features parapodia-like organs. At the same time, it also shows tracheal respiration and an open circulatory system, which are characteristics typically found in arthropods. Peripatus serves as a connecting link between these two groups, highlighting the evolutionary relationship between annelids and arthropods.
Q5. Define heredity. Explain the mechanism of hereditary changes.
Ans:-Heredity can be defined as the process of transmitting genetic information from parents to offspring through the mode of reproduction. It involves the passing on of traits and characteristics from one generation to the next. The mechanism of hereditary changes is influenced by various factors:
1. Natural Selection: Natural selection is a process where certain traits or alleles become more prevalent in a population because they provide a survival advantage.
2. Genetic Drift: Genetic drift refers to the random changes in allele frequencies within a population due to chance events.
3. Mutations: Mutations are sudden and inheritable changes in the genetic material, specifically in the DNA sequence of genes.
4. Recombination: Recombination occurs during meiosis, where genetic material is exchanged between homologous chromosomes.
These mechanisms collectively contribute to the hereditary changes observed in populations over time. Through natural selection, genetic drift, mutations, and recombination, genetic variations arise and can be passed on to subsequent generations. The cumulative effect of these hereditary changes is an essential component of the evolutionary process.
6. Define vestigial organs. Write names of some vestigial organs in human body and write the names of those animals in whom same organs are functional.
Ans:- Vestigial organs are degenerated or underdeveloped organs in organisms that have lost or reduced their original function throughout the course of evolution. These organs do not serve any significant purpose in the current organisms. While natural selection favors the elimination of vestigial organs, it may take millions of years for them to completely disappear.
Interestingly, vestigial organs in one animal may still be functional in other related species, demonstrating their varying usefulness. For example:
1. Appendix: The appendix in humans is considered vestigial as it has lost its apparent function. However, in ruminant animals like cows and goats, the appendix plays a role in the digestion of cellulose-rich diets.
2. Tailbone or Coccyx: The coccyx is a small bone at the end of the vertebral column in humans, representing the remnants of a tail. While it has lost its original function, it still serves as an attachment point for certain muscles and ligaments. In other animals, such as some primates, the tail remains functional.
3. Wisdom Teeth: Wisdom teeth, also known as third molars, often fail to emerge properly in humans due to changes in jaw size and diet. These vestigial teeth can cause dental issues. However, in some other mammals, such as certain primates, wisdom teeth serve a functional role in chewing and processing their diet.
4. Body Hair: Human body hair is considered vestigial as it no longer provides significant insulation or protection. However, it still exists in a reduced and fine form on our bodies. In other mammals, body hair is important for insulation, camouflage, or sensory functions.
Q7. Answer the following questions.
A. How are the hereditary changes responsible for evolution?
Ans:- Heredity plays a significant role in the process of evolution. Hereditary changes, also known as genetic variations, are responsible for the diversity observed in living organisms and the occurrence of evolutionary changes over time. These changes can be passed from one generation to the next, leading to the gradual transformation of species and the emergence of new traits and characteristics.
1. Genetic Variation: Hereditary changes, such as mutations and genetic recombination, introduce new variations in the genetic material of organisms.
2. Natural Selection: Hereditary changes influence an organism's fitness or its ability to survive and reproduce in a given environment.
3. Adaptation: Hereditary changes that confer advantages in specific environmental conditions increase an organism's likelihood of survival and successful reproduction.
4. Speciation: Hereditary changes, particularly when coupled with factors such as geographic isolation and reproductive barriers, can lead to the formation of new species.
hereditary changes provide the raw material for evolution by introducing genetic variations. Natural selection acts upon these variations, favoring advantageous traits and leading to the gradual evolution of populations and the emergence of new species. The interplay between hereditary changes and natural selection drives the diversity and complexity of life on Earth.
B. Explain the process of formation of complex proteins.
Ans:- Proteins have a quaternary structure, consisting of two or more polypeptide chains. Complex proteins are formed by the association of multiple protein molecules, held together by non-covalent bonds. The building blocks of proteins are amino acids, which join together to form a primary structure known as a polypeptide chain. The polypeptide chain can adopt secondary structures such as beta sheets or alpha helices. These secondary structures then fold into a three-dimensional arrangement, referred to as the tertiary structure. In some cases, proteins may interact with non-protein components, leading to the formation of a quaternary structure known as a complex protein.
C. Explain the theory of evolution and mention the proof supporting it.
Ans:- The theory of evolution is a scientific explanation for how life on Earth has changed and diversified over time. It states that all living organisms share a common ancestry and have descended from a common ancestor through a process of gradual modification and adaptation. The theory proposes that these changes occur through the mechanisms of variation, inheritance, and natural selection.
1. The fossil record provides a rich source of evidence for evolution. Fossils are the preserved remains or traces of ancient organisms.
2. The comparison of anatomical structures among different species reveals both similarities and differences. Homologous structures are those that have similar basic anatomy but may have different functions.
3. The study of DNA and molecular biology has provided compelling evidence for evolution.
4. The distribution of species across different geographic regions also supports the theory of evolution.
5. Experimental studies, such as the observation of natural selection in action and the breeding of domesticated plants and animals, provide direct evidence for evolutionary processes.
These are just a few examples of the extensive evidence supporting the theory of evolution. Collectively, the evidence from paleontology, comparative anatomy, molecular biology, biogeography, and experimental observations provides a strong scientific foundation for the theory of evolution.
D. Explain with suitable examples importance of anatomical evidences in evolution.
Ans:- Anatomical evidence plays a crucial role in understanding and supporting the theory of evolution. It involves comparing the physical structures and arrangements of different organisms to identify similarities and differences.
1. Homologous Structures: Homologous structures are anatomical features that have a common evolutionary origin but may have different functions in different species. The presence of homologous structures suggests that organisms share a common ancestor.
2. Vestigial Organs: Vestigial organs are structures that have lost their original function over the course of evolution. They are remnants of ancestral traits that no longer serve a purpose in the organism's current form or lifestyle.
3. Analogous Structures: Analogous structures are anatomical features that have similar functions but have evolved independently in different species. These structures do not share a common evolutionary origin but have evolved separately to adapt to similar environmental challenges.
4. Embryological Similarities: Embryological development provides valuable insights into the evolutionary relationships between different organisms. Many organisms, especially vertebrates, exhibit similarities in their early developmental stages.
E. Define fossil. Explain importance of fossils as proof of evolution.
Ans:- Fossil: A fossil is the preserved remains, impressions, or traces of past organisms that have been naturally preserved in rocks or sediments. Fossils can include the remains of plants, animals, and even microorganisms. They provide a valuable record of life on Earth and offer insights into the history of biological evolution.
Importance of Fossils as Proof of Evolution:
1. Fossils provide evidence of species that once existed but are now extinct. By studying these fossils, scientists can reconstruct the past biodiversity and track the changes in species over time.
2.Fossils often reveal transitional forms or intermediate stages in the evolution of organisms.
3.Fossils are found in layers of sedimentary rock, which are formed over time. By examining the relative position of fossils in these rock layers, scientists can determine the chronological order of species and their evolutionary history.
4.Fossils help in understanding the geographical distribution of organisms throughout history.
5.Fossils provide direct evidence of evolutionary relationships between species. By examining the similarities and differences in fossilized skeletal structures, scientists can determine the evolutionary connections between different species and establish their phylogenetic relationships.
F. Write evolutionary history of modern man.
Ans:-The evolutionary history of modern humans, Homo sapiens, spans millions of years. It is believed that our lineage diverged from the common ancestor we share with other primates around 6 to 7 million years ago.
1. Australopithecus: Around 4 to 2 million years ago, the Australopithecus genus emerged in Africa. These early hominins, such as Australopithecus afarensis (represented by the famous fossil "Lucy"), walked upright and showed some primitive human-like traits.
2. Homo habilis: Around 2.5 to 1.5 million years ago, Homo habilis appeared. This species is considered one of the earliest members of the Homo genus and was known for using primitive stone tools.
3. Homo erectus: Homo erectus lived from around 1.9 million years ago to about 140,000 years ago. They had larger brains and more advanced tools, and were the first hominins to migrate out of Africa, spreading to other parts of the world.
4. Homo neanderthalensis: Neanderthals, our closest extinct relatives, lived in Europe and parts of Asia from around 400,000 to 40,000 years ago. They had a robust build, larger brains, and exhibited cultural behaviors.
5. Homo sapiens: Modern humans, Homo sapiens, emerged in Africa around 300,000 to 200,000 years ago. They had larger brains, more advanced tools, and exhibited complex social and cultural behaviors. Modern humans gradually migrated out of Africa around 70,000 to 60,000 years ago, eventually populating the entire globe.
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