A Closer Look at the Animal Kingdom

A Closer Look at the Animal Kingdom — page 1 — nimals are everywhere Even busy New York City full of cars and concrete is teeming with animal life Ants march up a sidewalk Pigeons peck at crumbs while squirrels search for nuts A horse drawing a carriage trots by Boston terriers dragging their owner to the dog park A gray rat skitters across sub way tracks while a cat stares down from a skyscraper at tiny taxis and people below pe No matter where you live you will be sur rounded by animals including human beings This book will help you learn more about your fellow members of the animal kingdom There are more than ten million kinds of animals in the world and about 1 3 mil lion have been identified by scientists All life forms started in the same place in the oceans some 3 5 billion years ago Our com mon ancestors were simple single celled organisms Over time many living things became more complex as they adapted to various environments Multicellular organisms began to form and separate into different species as they moved Some moved into freshwater others to

A Closer Look at the Animal Kingdom — page 2 — INTRODUCTION Members of the kingdom Animalia are different from all other living things on Earth We are eukaryotes which means that our cells have various complex parts such as a nucleus and organelles Bacteria and archaea are made up of simpler prokary otic cells But unlike plants which are also eukaryotes we cannot make our own food through the process of photosynthesis animals must rely on eating vegetation and other animals to survive Animals are meta zoans the prefix meta means many because they are made of many cells Single celled animal like creatures are called protozoa Scientists who study animal life classify animals based on their bodies That helps scientists decide how animals are related to others One of the most important ways of MN classifying animals is by whether they are invertebrates who lack a backbone or ver tebrates who have one Invertebrates make up 95 percent of animal species The first animals were invertebrates such as sponges and jellyfish About 85 percent of inver tebrates are arthropods the word means jointed foot Many arthropods have an exoskeleton made of a substance called

A Closer Look at the Animal Kingdom — page 3 — A CLOSER Look AT THE ANIMAL KINGDOM Cygnets baby swans walk in the rain at Abbotsbury Swannery in Weymouth England The swannery is home to a herd of 8oo wild swans Matt Cardy Getty Images

A Closer Look at the Animal Kingdom — page 4 — INTRODUCTION I D chitin Arthropods include centipedes spiders scorpions and lobsters Most signifi cantly they include insects More than one million insect species have been identified the largest group within the animal kingdom Vertebrates are ani mals with backbones Some live in the sea such as fish others live on land others like birds take to the air They make up only about 5 percent of all animal species The complexity of their bodies lets vertebrates have bigger more com plex brains The most advanced vertebrates are mammals Only 5 000 species of mam mals exist The blue whale is a mammal that is the largest living

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