In: Biology
1. What are three factors that affect the abundance of
fossils?
2. What are three characteristics of the skeletons of vertebrate
animals (such as a dog, cat, horse, or primate) that suggest they
represent homologous structures? What is a homologous
structure?
3. Why do the fossils of whales and their ancestors support the
idea that whales evolved from a four-legged terrestrial vertebrate
mammal?
1.Factors that affect the abundance of fossil are
a.sedimentary rocks - Sedimentary rocks are a great place to find fossils. But if a sedimentary rock is heated, and metamorphosed, the heat will usually destroy the fossils.
b. Diagenetic processes - Diagenesis is the process that describes physical and chemical changes in sediments caused by increasing temperature and pressure as they get buried in the Earth's crust.Grains of sediment, rock fragments and fossils can be replaced by other minerals during diagenesis.
c. Taphonomic conditions - Depositional environments with high sedimentation rates are often associated with tectonic deformation (folds and faults).Hard things like bones and wood are easier to preserve than soft things, like skin or hair.
2. Homologous structures are organs or skeletal elements of animals and organisms that, by virtue of their similarity, suggest their connection to a common ancestor. These structures do not have to look exactly the same, or have the same function.
Forelimbs of vertebrates, where the wings of bats and birds, the arms of primates, the front flippers of whales and the forelegs of four-legged vertebrates like dogs and crocodiles are all derived from the same ancestral tetrapod structure. They all have similar plan of development but modified during evolutionto serve different function.The tailbone in human beings is so-named because it is a homologous structure to the beginning of many animals' tails, such as dogs, cats , monkeys. It is known as a "vestigial structure" because it is the last vestige of what was once a tail. This structure serves as evidence of having a common ancestor, one that would have had a tail.
3. Hippos likely evolved from a group of anthracotheres about 15 million years ago, the first whales evolved over 50 million years ago, and the ancestor of both these groups was terrestrial. These first whales, such as Pakicetus, were typical land animals. They had long skulls and large carnivorous teeth. Fossils of gigantic ancient whales called Basilosaurus were first mistaken for dinasaur fossils but were later recognised as mammals. These prehistoric whales were more elongated than modern whales and had small back legs and front flippers. Their nostrils were situated halfway between the tip of the snout and the forehead and they had earbones just like those of modern whales. Basilosaurus shows the link or intermediate between whales and their terrestrial ungulate ancestors mammals.