Answer:
1- Option A) describes an index fossil. Trilobite existed for a short time, but was abundant and lived in many locations.
2- Option B) Continents were once joined and have since drifted apart.
Explanation:
1) Fossils are animal and vegetable rests found in different strata of sedimentary rocks. Sedimentary layers deposit chronologically, so they are used to reflect history. They keep in each layer some of the forms of life that inhabited that area in the past. These fossils turn to be very useful while dating ages. The term Index fossils refer to those fossils that only existed in a given era or geological period during evolution.
Index fossils must:
• Be easily recognizable and distinguishable from all the other fossils
• Have lived in a relatively short geological period
• Present a wide geographic distribution
• Have lived in different sedimentary basins
• Appear in different types of rocks
• Be abundant
<em>A) Trilobite existed for a short time, but was abundant and lived in many locations. </em>The species accomplish the requirements. It is easily recognizable, had a wide geographic distribution, was abundant, and lived for a short time.
2) The tectonic plates theory states that there is a continual movement of the crust. It explains the movement of the different plates and their directions and interactions. The continental drift theory explains how these movements have been taking place since millions of years ago. When continents were together in a unique continent, many species used to inhabit it. When plates started to separate, they took some of these species that got apart by the ocean. Some species were already dead and fossilized, while some other organisms died during continental drift and got fossilized after the divergence. <em>The existence of the same fossils, placed in the same layers and of the same age, suggests that they used to inhabit the same area and died during the same time, meaning that continents were together when they got fossilized. </em>
Answer: due to insufficient exocytosis in the type II alveolar cells
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The correct statements are C and F.
There are two elementary types of pigments, which are responsible for the color of the coat, that is, phaeomelanin and eumelanin. Eumelanin is basically a black pigment and cells produced by it are responsible for a black dog coat color. However, there are genes that result in changes in eumelanin to produce brown, gray, or dusty pale brown coat color. The genes responsible for this change leads to the modifications in the creation of the eumelanin in the cells.
Due to this reason, dusty pale brown and gray dogs are considered as dilutes. Eumelanin can also be witnessed in eyes and nose. On the basis of the genes in dogs, the nose can be brown, black, dusty pale brown, or gray. The other pigments, that is, phaeomelanin is red. Most of the dogs exhibit both phaeomelanin and eumelanin, and the manner in which these two pigments get amalgamated is controlled by agouti locus.
The white color in dogs is not stimulated by any pigment, but by the cells that do not possess the capability to produce any kind of pigment. The entire animal can be affected in a different manner to albinos, or it can be restricted like the white coat patterns.
The correct statements regarding the mode of inheritance of the coat color genes are:
1) One of the genes modifies the expression of the other.
2) One of the genes is autosomal, and the other is X-linked.
