Animals.docx

https://basicbiology.net/animal

ANIMALS Animals are the most advanced organisms on the planet. The first animals are thought to have evolved over 550 million years ago and they have since spread to all corners of the globe and diversified into millions of species. Animals can be distinguished from other living things by the combination of three features: 1) they are unable to make their own food; 2) they have multiple cells; and each cell has a nucleus and other specialized structures called organelles. Scientifically put, animals are heterotrophic, multicellular organisms with eukaryotic cells. Animal species are often split into vertebrates and invertebrates – two very broad categories of animals. Vertebrate species are animals that do have a backbone such as humans, birds, fish and reptiles and make up the majority of large land animals. Invertebrate animals lack a backbone and often have a skeleton on the exterior of the body. The majority of animal species are classed as invertebrates and many you will be familiar with such as insects, jellyfish, worms and spiders.

Mammals are a group of warm-blooded vertebrates and include the largest and smartest animals on the planet. They are distinguished from other animals by having hair or fur and mammary glands for milk production.

Reptiles are a group of animals that include snakes, lizards, crocodiles, turtles and tuatara. They are an ancient group of cold-blooded, egg laying vertebrates with scales or scutes rather than fur or feathers.

Birds are a class of animals known as Aves and are easily distinguished by their feathers and wings. They have an incredible ability to fly and often perform amazing migrations over hundreds and even thousands of miles.

Fish are a group of aquatic animals with skulls, gills and digit-less limbs. Fish were the first vertebrate animals to evolve and there is now more than 30,000 species living on Earth. The highest diversity of fish is found in tropical coral reefs.

An invertebrate is any animal without an internal backbone such as insects, shellfish, worms, and spiders. Invertebrates are incredibly diverse and make up roughly 95% of all animal species.

MAMMALS Mammals are a group of warm-blooded vertebrate animals and include the largest animals on the planet. They are distinguished from other animals by having hair or fur and mammary glands for milk production in females. Mammal animals evolved on land and are mostly four-legged animals but a number of species have moved back to the sea or evolved to life in the air and in trees. Mammals are a class of animals that includes a wide range of different species. Most species fall into a group known as placentals. Placental mammals all help their unborn young develop in the womb by supplying food through a placenta. Placental mammals include animals such as rodents (mice, squirrels), carnivora (cats, dogs, bears), primates (humans, monkeys) and many more. Non-placental mammals belong to a group called marsupials, such as kangaroos and opossums, and they do not feed their developing young via a placenta. Mammals are considered to be the most intelligent group of organisms on Earth. Humans, in particular, are the epitome of intelligent organisms. Other clever mammal groups include primates, elephants, whales, and dolphins.

Primates are a group that includes apes, humans, lemurs, lorises, monkeys and tarsiers. They have grasping hands and feet with nails rather than claws. Primates are the only mammals found on all seven of Earth’s continents.

Rodents are a large group of well-known animals such as rats, mice, squirrels, and chipmunks. Rodents have a set of constantly growing front teeth. They must continually gnaw on food and wood to stop their front teeth from growing too long.

Bats have long been the victims of a misguided reputation as unpleasant animals. The vast majority of species feed only on plants and insects and pose no threat to humans or any other large animals. Bats

use echolocation to see objects in the dark and are the only mammals with the ability to fly.

Mammals, which evolved on land, made their way into water some millions of year ago to take advantage of what the sea has to offer. Marine mammals include a range of water-dwelling animals such as seals, walruses, sea otters, whales, dolphins, dugongs, and manatees.

Ungulates are a group of large mammals that are distinguished from other mammals by the presence of hooves. They are an extremely well-known and economically important group that include animals such as horses, cows, goats, deer, pigs plus many more.

Mammals are separated into two distinct evolutionary lines: the marsupials and the placentals. Marsupials are named after the abdominal pouch,

called a ‘marsupium’, in which their young live while they are suckling. Marsupials are quite different to other mammals.

The carnivorans are an amazing group of animals that share a special connection with humans. They are all related by a distant relative who evolved to eat meat. The carnivorans include animals such as cats, dogs, bears, seals, mustelids plus many other well-known animals.

Mammals have well-developed skeletons and although there is a wide range of differences between mammal species, the main structure of mammalian skeletonsfollow the same patterns. The skeleton can be separated into the head and body or axial and appendicular skeletons.

REPTILES Reptiles are a group of animals that include snakes, lizards, crocodiles, turtles and tuatara. They are coldblooded, egg laying vertebrates with scales or scutes rather than fur or feathers. The study of reptiles is known as herpetology which also includes the study of amphibians such as frogs and newts. Reptiles are an ancient group of vertebrate animals and we have a fossil record of reptiles stretching back to over 300 million years ago. Various reptiles are found on every continent on Earth apart from Antarctica. The overall global status of reptiles is unhealthy and numbers for many species are in decline. The main causes of their decline are habitat loss, invasive species, pollution and climate change.

Lizards are a group of scaly reptiles and are the most diverse group of all reptiles. They usually have four legs, long bodies, tails, eyelids and external ears. Well-known lizards include geckos, iguanas, skinks and chameleons.

Turtles are an ancient group of reptiles who have unique shells that protect their bodies. This group includes sea turtles, freshwater turtles and the land-based tortoises. Being reptiles, all turtles lay eggs on land and breathe air.

The crocodiles are stealthy predators and insight fear around the world. They live a semi-aquatic lifestyle and hunt in water, sitting and waiting to ambush their prey. Crocodiles are solidly built animals with short limbs and large, flattened mouths.

Snakes are limbless, elongated reptiles that have evolved from lizards. They are all carnivorous animals and many species produce venom that

helps to kill their prey. Of the 3,500 species of snakes around the world, around 600 are venomous.

The tuatara (Sphendon punctatus) is the sole surviving species from an ancient lineage of animals. The tuatara is found only in New Zealand.

BIRDS Birds are a unique group of animals with an incredible ability to fly. They are unique from all other animals because they have wings and feathers. Birds are in fact descendants of dinosaurs and formal collective name for birds is ‘Aves’. The vast majority of bird species have the ability to fly, a skill made possible through the evolution of wings, feathers and a number of other adaptations. A number of birds however, such as penguins and ostriches, have lost the ability to fly due to evolving in an environment where flying wasn’t necessary.

Birds are found all around the world, in almost any habitat, from the emperor penguins in the Antarctic to species found in some of the world’s hottest deserts. Some bird species spend their entire life in one small area while others migrate tens of thousands of miles every year. Their color, behavior and diversity is spectacular and it is difficult to find a more impressive sight than a bird gliding effortlessly on the wind.

A feather is a growth from the skin, much like a hair, and forms the plumage of a bird. It is an integral part of a bird’s biology. Feathers have evolved over millions of years to help with tasks such as flying and keeping warm.

For most people, flying is the activity that distinguishes birds from the plethora of animals on Earth. Birds are in fact one of three groups of animals that have evolved to take advantage of the 3-dimensional space of the Earth’s atmosphere.

Birds have a unique physiology that is often closely linked to the energetic demands of flying. As flying uses a lot of energy, they have high metabolisms, high body temperatures and an incredibly efficient respiratory system during flight.

Every year, hundreds of bird species all around the world complete migrations over both modest and magnificent distances. Over 10 billion birds travel between Europe, Asia, Africa, North America, South America and the South Pacific each year.

Penguins are a famous family of flightless birds. They are highly adapted to life at sea and are found in cooler waters of the Southern Hemisphere.

FISH Fish are a group of aquatic animals with skulls, gills and digitless limbs. They are separated into four groups: cartilaginous fish (such as sharks and rays), bony fish, jawless fish, and hagfish. Living in water presents a number of problems such as maintaining salt concentrations and neutral buoyancy and this group of animals has evolved a number of ways to deal with these issues. Fish were the first vertebrate animals to evolve and have since given rise to all the vertebrate animals found in water and on land. Fossils of fish have been dated back to the Cambrian period around 530 million years ago during a time when the diversity on Earth was going through a massive explosion. Currently, there are more than 30,000 species found around the world with the largest diversity found in coral reefs in the world’s tropical regions.

Sharks are the ultimate predators of the oceans and have developed many adaptations to help them hunt, reproduce and survive in their marine

environment. Sharks have a skeleton made from cartilage rather than bone.

Eels are fish with elongated, slender bodies. Around 800 species of eels are found all around the world. They have interesting life cycles and complete immense migrations between the freshwater and the oceans.

Just like all other animals, fish need oxygen to survive. Instead of breathing air into lungs, they have gills that absorb oxygen directly out of the water as they swim. Most fish species have four gills found on either of their head.

No group of fishes has conquered the sea more than the teleosts. They are the most advanced of all fishes and are dominant in both marine and

freshwater habitats. An incredible diversity of teleosts are found throughout the world.

Life in a river isn’t always easy but river fish thrive in the free-flowing conditions of rivers due to some key adaptations.

INVERTEBRATES An invertebrate is any animal without an internal backbone which includes animals such as insects, crustaceans, worms, jellyfish and sponges. The diversity of invertebrate species far outnumbers that of the vertebrate animals. One group of invertebrates called Arthropods, which includes insects, spiders and crustaceans, contains almost 80% of all animal species. The remaining invertebrates constitute between 12-15% of all animal species. The first invertebrates are believed to have evolved between 650 and 540 million years ago from single-celled organisms similar to certain cells found in sponges. Since then, they have diversified and spread into almost all environments on Earth and have evolved into some very sophisticated

animals. Invertebrates use a range of methods for reproduction, sourcing food and surviving – the success of their methods is evident by the sheer number of invertebrates that exist on Earth today.

Insects are a class of invertebrate animals and include a majority of all the world’s animal species. They are a massively successful group and include animals such as bees, butterflies, cockroaches, flies, mosquitoes, and ants.

Spiders are a group of land-dwelling, carnivorous invertebrates. They differ from insects by having only two body segments rather than three, eight walking legs rather than six and no antennae. Spiders have jointed limbs and a hard external skeleton.

Crustaceans are mostly marine invertebrates and are closely related to spiders and insects. Crustaceans include animals such as crabs, barnacles, lobsters, shrimp and many species of zooplankton.

Molluscs are a phylum of mostly marine invertebrates that includes octopus, mussels, clams, snails, squid, and many more animals. They have a muscular ‘foot’, a mantle which produces a shell and internal organs.

ARTHROPODS Arthropoda is a phylum of animals that includes many well-known invertebrates such as insects, crustaceans, spiders, centipedes, and scorpions. They are distinguished by their hard external skeleton or shell and jointed limbs.

WORMS Worms are invertebrates from a variety of distantly related animal groups. They are primitive animals with elongated bodies, a mouth, gut, anus and they are usually limbless. Common worms include flatworms, earthworms, and polychaetes.

SPONGES Sponges are only just classed as animals and are believed to be one of the first animals to have evolved. A single sponge cell can survive and reproduce to create a colony of sponge cells that work together as a multicellular animal.

MORE ABOUT ANIMALS! https://kids.nationalgeographic.com/animals/