Evolution

Natural selection is a process by which an organism gets adapted to its environment by making selective changes in its genetic constitution. The unit of natural selection is an individual since genes work at an individual level.

Natural selection occurs to maintain the survival of a species by making favourable changes in its genes that helps it cope up with the changing environment. These changes are heritable and are passed on to the subsequent generations eventually leading to evolution. In the process of natural selection, organisms with more favourable changes will only survive and reproduce.

Let's evaluate each statement in detail:

Cuscuta is a chlorophyllous endoparasite:

• This is incorrect. Cuscuta, commonly known as dodder, is an epiparasite, meaning it attaches to the outside of a host plant and absorbs nutrients. It lacks chlorophyll and cannot perform photosynthesis. Therefore, it is a parasitic plant, but not an endoparasite, and it is not chlorophyllous.

The human liver fluke needs only one host to complete its life cycle:

• This is incorrect. The human liver fluke (Fasciola hepatica) requires two hosts to complete its life cycle. The first host is usually a snail, which is an intermediate host, and the second host is typically a mammal (like a human), which is the definitive host. The fluke's larvae are released into water where they infect snails, and then the snails release larvae that infect mammals, including humans.

The life cycle of an endoparasite is more complex due to their extreme specialization:

• This is correct. Endoparasites (parasites living inside the host) exhibit extreme specialization to survive within the host's body. Their life cycles are often more complex because they may involve multiple stages, different hosts, and specialized mechanisms to evade the host's immune system. For example, the human liver fluke (Fasciola hepatica) has a complex life cycle involving different larval stages and host organisms.

During the course of evolution, the host bird's eggs have evolved to resemble the eggs of the parasitic bird:

• This is correct. This phenomenon occurs in brood parasitism. A parasitic bird, like the cuckoo, lays its eggs in the nests of other bird species. Over time, the parasitic bird's eggs have evolved to resemble the eggs of the host species in color and pattern, helping the parasitic bird's eggs go unnoticed, increasing the chances of the host bird incubating them.

The correct statement is only statement 3 because the life cycle of endoparasites is indeed more complex due to their extreme specialization.

So, the correct answer is (C): Only 3

The question asks for the *first* human-like being. To answer this, we need to consider what characteristics define "human-like" and how different hominin species evolved.

Understanding Hominin Evolution:

Hominins are members of the tribe Hominini, which includes modern humans and all of our extinct ancestors after the split from the chimpanzee lineage. Key features that evolved over time and make a species more "human-like" include:

• Bipedalism: Walking upright on two legs.
• Increased Brain Size (Encephalization): Larger brain capacity relative to body size.
• Tool Use: Creating and using tools.
• Dietary Changes: Shift towards more varied diets, including meat.
• Social Complexity: More complex social structures and behaviors.

Analyzing the Options:

• Homo menthus: This is not a recognized or valid species name in the scientific study of human evolution. Therefore, it is incorrect.
• Homo erectus: Homo erectus is an important hominin species that lived from about 1.89 million to 110,000 years ago. They are known for having a larger brain size than earlier hominins, using fire, and migrating out of Africa. While more human-like than earlier species, they weren't the *first* to display key human-like traits.
• Homo habilis: Homo habilis lived from approximately 2.3 to 1.4 million years ago. The name "habilis" means "handy man," because fossil evidence suggests they were among the earliest hominins to use stone tools. They had a slightly larger brain size than their predecessors (like Australopithecus), though still smaller than Homo erectus. Their tool use and slightly increased brain size are significant steps towards human-like characteristics.
• Homo sapiens: Homo sapiens are modern humans. While obviously the most human-like, they are not the *first* species to display human-like traits.

Why Homo habilis is the best answer:

While earlier hominins like *Australopithecus* were bipedal, *Homo habilis* is generally considered the first to combine bipedalism with evidence of tool use and a somewhat larger brain. This combination of characteristics places them as the earliest recognized species within the *Homo* genus, and arguably the *first* exhibiting a suite of characteristics we associate with "human-like" behavior, even if those traits were still relatively primitive compared to later species like *Homo erectus* or *Homo sapiens*.

Therefore, the best answer is: Homo habilis