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:
The species that develop in aquatic environments, need to be able to have an adequate locomotion and according to the hydrostatic pressure in the water, which this pressure has the opposite direction to gravity in terrestrial life.
Explanation:
Vertebrates that have a skeleton are accustomed to gravitational forces, and this bone structure is what allows adequate locomotion to perform movements as a function of the force of earth's gravity, in water the force of gravity has no effect, since that the hydrostatic force predominates, which the direction is opposite to the gravitational forces.
Amorphous bodies, with few solid structures, not bony, make them better adapt to movements in water masses that are promoted by hydrostatic forces.
Answer:
b. giving birth to live young (viviparous)
Explanation:
Monotremes include duck-billed platypus and few other mammalian species that are oviparous. These mammalian species do not give birth to young ones, that is, they are not viviparous. Rather they lay eggs and are oviparous.
These species are also characterized by the absence of teeth. The primitive monotremes also exhibit external fertilization.
Examples of egg-laying mammals include anteaters or echidnas and the duck-billed platypus. The laid eggs are carried by females in an abdominal ouch to keep them warm.
Progesterone.
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