Studying for my final can someone please answer a couple of intro to evolutionar
ID: 73660 • Letter: S
Question
Studying for my final can someone please answer a couple of intro to evolutionary Bio questions. It does not have to be detailed just general picture would be great. Any help would be greatly appreciated.
1. What are the classes of macromolules? How do they compare?
2.Origin of life, evolution of eukaryotes, multicellularity
3.What were key evolutionary radiations
4.What are the various roles played/niches occupied by organisms on Earth?
5. What key features led to invasion of land by plants and animals?
6.How have phototrophs evolved from cyanobacteria to algae to non-vascular plants to vascular plants to seed plants?
7.Understand role mitotic vs. meiotic divisions play in organismal growth/reproduction and how they explain Mendel’s laws
Explanation / Answer
1.
Carbohydrates, proteins, fats and nucleic acids are the biomolecules occurring in a cell. Each biomolecule is specified for a distinct role in the cell.
Carbohydrates are high energy molecules and are readily broken down in a cell to provide energy in the form of ATP. The simple sugar available in a cell is glucose. All the other types of sugars are converted to glucose and are break down. Glucose forms a polymer called glycogen and acts as energy reserve in a cell. The glycogen reserves occur in liver and muscles and are ready sources of energy.
The proteins are polymers of amino acids. These are building blocks of energy. The proteins contribute for the muscle mass and also various proteins having specific role of transport and compositions of cellular constituents.
Lipids or fats are chief sources of a cell. Various kinds of lipids and fats form structural and other components in a cell. The fats provide insulation to body cells and also act as energy reserves. When the glucose is no longer available as energy resource in a cell, the cells use fats and breakdown then to meet the energy requirements. Fats accumulate in the adipose tissue and also help in maintaining the body temperature.
Nucleic acids, the DNA and RNA are the genetic materials. These genetic materials are passed from parent to offspring during reproduction and fertilization. The genetic material is much essential for any cell to maintain its genomic integrity. The RNA is mainly involved in protein synthesis. The proteins required by a cell are synthesized from DNA to RNA and then into proteins through the processes of transcription and translation. The protein synthesis is also regulated by the RNA.
2.
The formation of a living cell from organic molecules has taken a long way. The formation of life from nonlife has greatest gap in the scientific theories of earth’s history. After the cooling of earth, some 200 to 300 billion years ago, the water cells similar to modern bacteria were formed from condensation of organic molecules into proteinoid microspheres under certain conditions.
These are not cells but have some characteristics of living systems. During the course of evolution first, simple RNA molecules might have formed which later had the characteristics of self replication, processing of other messenger RNA after transcription, helping in the replication of DNA, catalyzing the chemical reactions and might have led to formation of systems consisting of DNA directed protein synthesis.
The micro fossils discovered in the rocks more than 3.5 billion years old were the single celled prokaryotic organisms resembling the modern bacteria. These must have evolved in absence of oxygen. Over time, photosynthetic organisms might have evolved increasing the concentration of oxygen in the atmosphere. This has caused some organisms to extinct because they could not tolerate the high oxygen levels and some organisms to develop more effective metabolic pathways to metabolize the oxygen.
The prokaryotic cells evolved earlier were started to develop internal membranes some 2 billion years ago, due to which the evolution of eukaryotic cells had took place. The eukaryotic organelles like mitochondria and chloroplast resemble the prokaryotic cells. This has happened due to establishment of symbiotic relationship between prokaryotes that entered the eukaryotic cells. Thus, endosymbiotic theory states that the eukaryotic cells are produced from living communities formed by prokaryotic organisms.
It is evident the life is not formed spontaneously and this has been known by the proving of spontaneous generation theory as wrong by Louis Pasteur. Life arose from nonlife several billion years ago by the condensation of organic molecules. Still, life can be formed by nonlife by various chemical reactions by which artificial genetic molecules can be synthesized and evolution occurs through life to life forms.
6.
The evolution of the plants had thought to occur from fresh water green algae about 590 MYA (million years ago). The green algae are not plants but they contain chlorophyll a and b and other accessory pigments like plants. Like plants green algae also stored carbohydrates as starch and they also possess cellulosic cell walls like plants.
The green algae differ from land plants in the aspect of protection of zygote and its nourishment till the embryo is formed which is observed in the land plants. The green algae and land plants have some common DNA and RNA base sequences which suggest that land plants might have evolved and closely related to a specific group of fresh water green algae called charophytes.The charophytes and land plants form same clade on phylogenetic tree and are monophyletic group.
Bryophytes are the first land plants having roots, stems and leaves. In a strict sense the roots, stems and leaves are well supported by vascular tissue that transports water and nutrients throughout the plant body. But, bryophytes lack the vascular tissue and hence are known as non vascular plants. The bryophytes are low lying and can grow up to maximum height of 20cm.
Bryophytes share some characteristics with vascular plants like alteration of generations in life cycle, the plant body covered by cuticle and stomata appear in hornworts and mosses. The complex apical tissue and male and female reproductive structures producing flagellated sperm and eggs are similar to higher plants but in bryophytes the gametophyte is dominant.
Lycophytes are the first vascular plants containing stem, leaves and roots. The leaves are known as microphylls containing single strand of vascular tissue. They are evolved as side extensions of the stem. The roots are lower extensions of the stem. Lycophytes are commonly known as club mosses containing three groups: ground pines (Lycopodium), spike mosses (Selagenella) and quillworts (Isoetes). In Lycopodium a cone shaped structure called strobilus occurs at the top of the plant body.
Pteridophytes are seedless vascular plants containing three types including ferns and their allies, horse tails and whisk ferns. Ferns are wide spread and contain about 11000 species. They are grown in warm, moist and tropical regions. They can also grow in temperate regions of Arctic Circle. They can grow up to 20 meters height. The megaphylls of ferns are called as fronds that are broad and subdivided into leaflets. The sporangia occur in cluster called sori on underside of the fronds. The sori are covered by thin protective structure called indusia.
The gymnosperms contain four groups called conifers, cycads, ginkgoes and gnetophytes. All these plants have seeds that are naked and not enclosed by fruit.
Gymnosperms have cones that bear the seeds. Angiosperms and gymnosperms are the large plants from which the fiber and wood are obtained. The gymnosperms exhibit narrow leaves and naked ovules. They are the ever green trees found in the ever green rain forests.
The angiosperms represent the small ornamental plants to the large tree. They are the flowering plants and possess broad leaves. The angiosperms are divided in to two groups called monocots (which contain a single cotyledon in the embryo) and dicots (which contain two cotyledons in the embryo).