Biology Test-6

In co-dominance, F1 hybrid both alleles expressed themselves equally and there is no mixing of the effect of both of the alleles, and thus, hybrid progeny (F1) resemble both parents. The alleles which do not shows a dominant-recessive relationship are able to express themselves independently, when present together are called codominant alleles.

ABO blood group is an example of codominance-

The structure in a different organism which is not similar anatomically though they perform a similar function are called analogous organ.

The anatomically different structure evolved towards the same direction due to adaptations to similar habitat. This is the called the convergent evolution because anatomically dissimilar and origin wise different structure converged towards the common function. Thus, the analogous structure is the result of convergent evolution.

Stabilizing selection: If nature favours that individual in the population which possess the mean character value, then that natural selection leads to stabilization of the trait. In this, the peak gets higher and narrow as the natures try to decrease the peripheral character value. 
Directional selection: If selections act to eliminate one extreme form and support the other extreme then shift the peak in one direction, which is selected by the nature. 
Disruptive selection: If the selection do not favours the mean character value, rather both the peripheral character values, then this kind of selection is called disruptive selection. In this, two peaks are formed at two extreme the curve and a kind of depression at the centre. 
Balancing Selection: Balancing selection refers to a number of selective processes by which multiple alleles (different versions of a gene) are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone.

Mendel selected 14 true-breeding pea plants varieties, as a pair was similar except for one character with contrasting traits. These characters are:

A + T = C + G is not correct according to Chargaff's rule.

According to Chargaff's rule, the total amount of adenine released is equal to the total amount of thymine and similarly, the total amount of cytosine is equal to total amount of guanine, i.e A = T and C = G. Therefore, the total amount of purines is equal to the total number of pyrimidines.

Therefore,

Purines = Pyrimidines

A + G = C + T

\(\frac{A+G}{C+T}=1\)

Individuals with type O blood do not produce ABO antigens. Therefore, their blood normally will not be rejected when it is given to others with different ABO types. As a result, type O people are universal donors for transfusions, but they can receive only type O blood themselves.

Herbarium, Zoological parks, Botanical garden and Key are the various taxonomical aids.

● Zoological parks, are ex situ conservation not the in - situ, in which animals are kept in protected environment which is made similar to their natural habitat as much as possible. Theses parks serves as an ideal means to study and learns different foods and habitat and behaviour of variety of various animals.

● Key is a taxonomical aid that helps in identification of plant and animal species. These keys are based on similarities and dissimilarities in characters, generally in a pair called couplet. It is of two types- Indented and Bracketed keys. Indented key provides a sequence of choices between two or more statements while in bracketed key, a pair of contrasting characters are used.

● Biological museums in plants and animal species are preserved in jars and containers with the help of appropriate preservatives. They may also be dried and preserved. Birds and larger animals are usually stuffed before preserving and insects are killed and pinned in boxes. We sometimes find skeletons of various animals too.

● Herbarium is a store that houses a collection of preserved plant species. Plant specimens are preserved in forms of herbarium sheets which are prepared by drying, pressing and preserving the samples on sheets. These sheets are then arranged in their order of classification in the taxonomic hierarchy.

Chara is the monoecious plant and is a green alga. The sex organ is highly specialised.

• The male sex organ is called globule and female sex organ is called as nucule, instead of antheridium and oogonium for male and female organ respectively.
• These sex organs are especially multi-celled and covered by the jacket.
• After fertilization, a diploid spore is formed. At the time of germination diploid oospore nucleus divides to make haploid nuclei and haploid Chara plant. Thus the life cycle of Chara a predominantly haploid type.

In secondary treatment remaining major part of sludge is pumped into large tanks called anaerobic sludge digesters. Here anaerobic methanogenic bacteria digest the bacteria and fungi present in sludge. Bacteria produces a mixture of gases like methane, hydrogen sulphide and carbon dioxide. These gases can be used as a source of energy as it is inflammable and forms the biogas.

Ribosomes are non-membrane-bound organelles and granular structure that was discovered by George Palade in 1953. They are composed of ribonucleic acid (RNA) and proteins. Ribosomes are protein synthesizers of a cell and they are found in both Prokaryotic and Eukaryotic cells. So, 'Palade particles' is another name for ribosomes.

The epidermis is the protective outer layer of clonally related cells covering all plant organs. It is made up of cellulose, hemicelluloses, and pectin.

Functions of the cell wall in the plant:

• Regulates and controls the direction of cell growth.
• Providing strength, structural support, and maintaining the shape of the cell.
• It supports the entry of smaller molecules moving freely.

Cell Membrane is present in all organisms including plants.

• It is also known as the plasma membrane.
• It is a semi-permeable membrane composed of lipids and proteins.

Taxonomic hierarchy refers to the sequence of categories in increasing or decreasing order. The kingdom is the highest rank and species is the lowest rank in the hierarchy.

Taxonomic Hierarchy Categories:

Following are the important taxonomic hierarchies in which different organisms are classified:

Kingdom:

The kingdom is the highest level of classification, which is divided into subgroups at various levels. There are 5 kingdoms in which the living organisms are classified, namely, Animalia, Plantae, Fungi, Protista, and Monera.

Phylum:

This is the next level of classification and is more specific than the kingdom. There are 35 phyla in the kingdom Animalia. For Example – Porifera, Chordata, Arthropoda, etc.

Class:

Class was the most general rank in the taxonomic hierarchy until phyla were not introduced. Kingdom Animalia includes 108 classes including class mammalia, reptilia, aves, etc. However, the classes used today are different from those proposed by Linnaeus and are not used frequently.

Order:

Order is a more specific rank than class. The order constitutes one or more than one similar family. There are around 26 orders in class Mammalia such as primates, Carnivora, etc.

Family:

This category of the taxonomic hierarchy includes various genera that share a few similarities. For eg., the families in the order Carnivora include Canidae, Felidae, Ursidae, etc.

Genus:

A group of similar species forms a genus. Some genera have only one species and is known as monotypic, whereas, some have more than one species and is known as polytypic. For eg., lion and tiger are placed under the genus Panthera.

Species:

It is the lowest level of the taxonomic hierarchy. There are about 8.7 million different species on earth. It refers to a group of organisms that are similar in shape, form, reproductive features. Species can be further divided into sub-species.

Oceans cover around 70% of Earth’s surface, so most precipitation falls right back into the ocean and the cycle of evaporation and precipitation begins again.

The presence of water vapor in the atmosphere is one of the things that makes Earth livable.

Like carbon dioxide, water vapor traps heat in the atmosphere and helps keep surface air temperatures on Earth in a habitable range.

Temperatures on planets without water vapor in the atmosphere, like Mars, stay as low as -100° C.

Evaporation and precipitation are balanced over Earth's surface. In other words, if evaporation increases, precipitation also increases.

The green pigment of the leaf is called Chlorophyll which has Magnesium(Mg) involved in its structure which imparts the green color of the leaf.

Some other pigments responsible for the color of the leaf are:

Peroxisomes are involved in photorespiration. Photorespiration is a wasteful process that occurs when RuBP binds to oxygen in presence of RuBisCO. There is no synthesis of sugars rather there is utilisation of ATP. Photorespiration occurs in three organelles - chloroplast, peroxisomes, and mitochondria.

Calvin cycle, CAM pathway, and C₄ cycle occur in chloroplasts.