The event that characterizes the Paleozoic era is the Cambrian explosion, according to which a large number of biological class prevalent today are primitive of fish and corals that evolved during that era.
Further Explanation:
The Paleozoic Era is run from nearly five hundred forty-two million years ago to two hundred fifty-one million years ago; that was the time many changes occur on earth. This era starts with the breakdown of the supercontinent and the formation of a new one. In this era, many plants are developed and also very first animal (vertebrate) found on land. This era is divided into six different periods, namely:
After this, many Paleozoic seas found with blastoid and crinoid echinoderms, rugose corals, tabulate, graptolites, and articulate brachiopods. At the last phase of this era, glossopterids, cycads, ferns, and primitive conifers were present across many landscapes. The Paleozoic mass disappears at the late phase of Devonian and end phase of Ordovician. The end phase of this era is referred to as the Permian period.
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Answer Details:
Grade: High School
Subject: Biology
Chapter: Evolution
Keywords:
Permian, Devonian, Ordovician, mass, Paleozoic era, blastoid, landscapes, sea, end phase, echinoderms, rugose.
chloroplast is right
During the process of vaccination, an attenuated pathogen is inserted into the body the organisms. The attenuated pathogen is able to provoke the primary immune response in the body of the organism without causing any harm.
Once the primary immune response is generated, the body creates a memory in form of antibody to the pathogen. After vaccination, if the pathogen infects, the body recalls the memory and generates a secondary immune response. The intensity of the secondary immune response is much higher than the primary one, so, as soon as the pathogen enter in the body, the antibodies against it are activated and result in defeating the infection.
For a better understanding purpose, the intensity of the primary and the secondary immune response is given in the figure:
Answer:
d. a vaccine causes the secretion of antibodies which remain in blood and fight the pathogen at the time of an infection.
Answer:
Binary fission.
Explanation:
Binary fission: It is known as the asexual reproduction, in which a single organism formed two independent organisms, and also defined as duplication of organisms. This starts with the replication process of DNA within the cell. Before binary fission mitochondria must have replicates its DNA.
After that, the DNA is separated into ends (alternate) of the single cell. One cell becomes two with the help of plasma membrane turns the cell apart. Then each cell is capable of all the function with fully functioning DNA molecule, and cell becomes independent organisms.
B. red giant stage
C. planetary nebula stage
D. black dwarf stage
Answer: B. red giant stage
When the sun runs out of fuel-hydrogen, its atmosphere expands and it becomes a red-giant star. The Sun would leave the main-sequence stage and enter the red-giant stage in which huge pressure generated in its core pushes the atmosphere outwards making it expand and nuclear fusion reaction of heavier nuclei starts. The end stage of Sun would be formation of a white dwarf.
Thus, from the given options, correct answer is B. red giant stage
The final stage in the sun's life cycle is the black dwarf stage. The black dwarf stage is proposed to be the final stage in the life cycle of a white dwarf, after it has exhausted its nuclear fuel and undergone gravitational collapse.
The correct option is D.
The life cycle of a star like the sun can be divided into several stages. The specific sequence of stages depends on the mass of the star. However, for a star like the sun, the stages are as follows:
Main Sequence: The sun is currently in the main sequence stage, where hydrogen fusion occurs in its core, producing energy.
Red Giant: As the sun exhausts its hydrogen fuel, it will enter the red giant stage. During this stage, the sun's core contracts while the outer layers expand, causing the sun to become larger and cooler.
Planetary Nebula: In the next stage, the sun will shed its outer layers, forming a glowing shell of gas and dust called a planetary nebula. This process exposes the core of the star.
White Dwarf: After the planetary nebula stage, what remains of the sun's core will collapse inward due to gravitational forces. Black Dwarf: The final stage in the sun's life cycle is the black dwarf stage.
Hence , D is the correct option
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