Apex predator in the context of "Orcas"

Marine life, sea life or ocean life is the collective ecological communities that encompass all aquatic animals, plants, algae, fungi, protists, single-celled microorganisms and associated viruses living in the saline water of marine habitats, either the sea water of marginal seas and oceans, or the brackish water of coastal wetlands, lagoons, estuaries and inland seas. As of 2023, more than 242,000 marine species have been documented, and perhaps two million marine species are yet to be documented. An average of 2,332 new species per year are being described. Marine life is studied scientifically in both marine biology and in biological oceanography.

By volume, oceans provide about 90% of the living space on Earth, and served as the cradle of life and vital biotic sanctuaries throughout Earth's geological history. The earliest known life forms evolved as anaerobic prokaryotes (archaea and bacteria) in the Archean oceans around the deep sea hydrothermal vents, before photoautotrophs appeared and allowed the microbial mats to expand into shallow water marine environments. The Great Oxygenation Event of the early Proterozoic significantly altered the marine chemistry, which likely caused a widespread anaerobe extinction event but also led to the evolution of eukaryotes through symbiogenesis between surviving anaerobes and aerobes. Complex life eventually arose out of marine eukaryotes during the Neoproterozoic, and which culminated in a large evolutionary radiation event of mostly sessile macrofaunae known as the Avalon Explosion. This was followed in the early Phanerozoic by a more prominent radiation event known as the Cambrian Explosion, where actively moving eumetazoan became prevalent. These marine life also expanded into fresh waters, where fungi and green algae that were washed ashore onto riparian areas started to take hold later during the Ordovician before rapidly expanding inland during the Silurian and Devonian, paving the way for terrestrial ecosystems to develop.

The orca (Orcinus orca), or killer whale, is a toothed whale and the largest member of the oceanic dolphin family. The only extant species in the genus Orcinus, it is recognizable by its distinct pigmentation; being mostly black on top, white on the bottom and having recognizable white eye patches. A cosmopolitan species, it inhabits a wide range of marine environments, from Arctic to Antarctic regions to tropical seas, but is more commonly documented in temperate or cooler coastal waters. Scientists have proposed dividing the global population into races, subspecies, or possibly even species.

Orcas are apex predators with a diverse diet. Individual populations often specialize in particular types of prey, including bony fish, sharks, rays, and marine mammals such as seals, dolphins, and whales. They are highly social, with some populations forming stable matrilineal family groups (pods). Their sophisticated hunting techniques and vocal behaviors, often unique to specific groups and passed down from generation to generation, are considered to be manifestations of animal culture. The most studied populations are off the west coast of North America, which include fish-eating "residents", mammal-eating "transients", and offshores.

A keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance. The concept was introduced in 1969 by the zoologist Robert T. Paine. Keystone species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. Some keystone species, such as the wolf and lion, are also apex predators.

The role that a keystone species plays in its ecosystem is analogous to the role of a keystone in an arch. While the keystone is under the least pressure of any of the stones in an arch, the arch still collapses without it. Similarly, an ecosystem may experience a dramatic shift if a keystone species is removed, even though that species was a small part of the ecosystem by measures of biomass or productivity.It became a popular concept in conservation biology, alongside flagship and umbrella species. Although the concept is valued as a descriptor for particularly strong inter-species interactions, and has allowed easier communication between ecologists and conservation policy-makers, it has been criticized for oversimplifying complex ecological systems.

The lion (Panthera leo) is a large cat of the genus Panthera, currently ranging only in Sub-Saharan Africa and India. It has a muscular, broad-chested body; a short, rounded head; round ears; and a dark, hairy tuft at the tip of its tail. It is sexually dimorphic; adult male lions are larger than females and have a more prominent mane that usually obscures the ears and extends to the shoulders.

The lion inhabits grasslands, savannahs, and shrublands. It is an apex and keystone predator, preying mostly on medium-sized and large ungulates. It is usually more diurnal than other wild cats, but when persecuted, it adapts to being active at night and at twilight. It is a social species, forming groups called prides. A lion pride consists of related females and cubs, and a few or one adult male who is unrelated to the females. Groups of female lions usually hunt together. Adult males often compete to keep or gain that membership in the pride.

A food chain is a linear network of links in a food web, often beginning with an autotroph (such as grass or algae), also called a producer, and typically ending at an apex predator (such as grizzly bears or killer whales), detritivore (such as earthworms and woodlice), or decomposer (such as fungi or bacteria). A food web is distinct from a food chain. A food chain illustrates the associations between organisms according to the energy sources they consume in trophic levels, and the most common way to quantify them is in length: the number of links between a trophic consumer and the base of the chain.

Studies of food chains are essential to many biological studies.

The trophic level of an organism is the position it occupies in a food web. Within a food web, a food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the number of steps it is from the start of the chain. A food web starts at trophic level 1 with primary producers such as plants, can move to herbivores at level 2, carnivores at level 3 or higher, and typically finish with apex predators at level 4 or 5. The path along the chain can form either a one-way flow or a part of a wider food "web". Ecological communities with higher biodiversity form more complex trophic paths.

The word trophic derives from the Greek τροφή (trophē) referring to food or nourishment.

The great white shark (Carcharodon carcharias), also known as the white shark, white pointer, or simply great white, is the largest living macropredatory shark and fish. It is a mackerel shark and closely related to the mako sharks, the porbeagle and the salmon shark. It is a robustly built species with a grayish upper-side and a white underside, the latter feature gives it its name. Females average 4.6 to 4.9 m (15 to 16 ft) while males average 3.4 to 4.0 m (11 to 13 ft). Females typically weigh 1,000–1,900 kg (2,200–4,200 lb) compared to 680–1,000 kg (1,500–2,200 lb) for males. They are estimated to reach a length close to 6.1 m (20 ft) and a weight of over 2,494.9 kg (5,500 lb). The shark has approximately 300 triangular, serrated teeth that are continuously replaced. Its massive, fatty liver can reach over a quarter of its body weight and provides buoyancy and energy. White sharks are unusual among fish in that they are warm-blooded, allowing them to remain active in colder waters.

White sharks inhabit tropical and temperate ocean waters around the world and can be found both along the coast and further out to sea. Populations are most concentrated at the Pacific and Atlantic sides of North America and in the waters of southern Africa and Oceania. They are a highly migratory species, traveling between the coast and open ocean and even between continents. The great white shark is an apex predator and preys on marine mammals such as pinnipeds and dolphins, as well as fish, including other sharks, and cephalopods. It is also a prolific scavenger of whale carcasses. Despite its apex predator status, the species itself is sometimes preyed on by orcas. White sharks are generally solitary but gather in aggregations, particularly at feeding sites. They may communicate and establish dominance hierarchies with body language. Reproductive behavior in the species is less understood, but it is known to be ovoviviparous; with pups hatching from eggs within the female, who gives live birth after 12 months. Juvenile white sharks typically inhabit shallower water and cannot eat marine mammals until they reach around 3 m (9.8 ft).