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Life Science. Chapter 27 Diversity of Life on Earth. The Main Idea. Earth is home to millions of living species, including one celled bacteria, giant redwood trees and animals like us. About 1.5 million known species live on earth.

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Life science

Life Science

Chapter 27

Diversity of Life on Earth

The main idea
The Main Idea

  • Earth is home to millions of living species, including one celled bacteria, giant redwood trees and animals like us.

  • About 1.5 million known species live on earth.

  • Many more- estimated to be anywhere between 10 - 100 million have yet to be discovered.

  • How do we keep track of all of this and make it easier to study?

27 1 classifying living
27.1 Classifying Living

Origin of current classification system

  • Originated by Carolus Linnaeus – 18th century

  • Came up with the division of the system: domain, kingdom, phylum, class, order, family, genus, species

Linnaeus continued
Linnaeus continued

  • Also came up with rules for how an organism is named

    • All species have a two-part scientific name made up of the genus name and the species name


      Homo sapiens – human (wise human)

      Canisfamiliaris– dog (intimate dog)


Rules for naming
Rules for naming

  • Genus name is always capitalized; species name is always lower case.

  • Italicize or underline scientific names.

Homo sapiens history
Homo sapiens history

  • Humans are primates. We belong to a group that also includes monkeys and apes.

  • Humans are also hominids, a group of primates that includes modern man (Homo sapiens) as well as some of our extinct relatives.


  • Humans are the only hominid species in existence today.

  • Fossil hominids provide clues as to how humans evolved.

Extinct hominids
Extinct Hominids

  • Earliest known hominids- belongs to the group Australopithecus (dated 3.2 million years old) fossil found called Lucy- 3 ft. 8 in. tall with a brain the size of a chimpanzee- but it is clear she walked upright.

  • Homo habilisfossils 2.2 million years old – larger brains, made stone tools (name means ‘handy man’), males much larger than females

Homo erectus
Homo erectus

  • Homo erectus fossils 400,000 – 2 million years old- even larger brains, skilled tool maker, first species to leave Africa and spread to Europe and Asia. Size differences between males and females slowly changed to make it closer to what it is today.

Homo sapiens
Homo sapiens

  • Neanderthals- Homo sapiens neandethalensis are closely related to modern humans

    • Lived 30,000 to 200,000 years ago

    • Thick muscles, brains about the same size as they are now, complex burial rituals and used plants to treat disease

  • Earliest fossils of modern human, Homo sapiens sapiens are from Ethiopia and are 195,000 years old

    • Cultural traits such as religion, art, music appeared only 50,000 years ago

    • There is a major gap that can’t be explained.

    • Scientists believe it was the evolution of language that allowed human culture to blossom 50,000 years ago.

Linnaean system species are grouped based on how similar they are
Linnaean system-Species are grouped based on how similar they are









27 2 evolution and classification
27.2 Evolution and Classification they are

  • Linnaeus came up with his classification system long before Charles Darwin published his theory of evolution

  • We now know that Earth’s species are the result of billions of years of evolution, including numerous instances of speciation. Knowing how speciation produced different species allos scientists to describe how different species are related.

Speciation they are

  • A species is a group of organisms whose members can breed with one another but not with members of other species and produce viable offspring (children that can produce offspring).

  • Speciation- the formation of new species- is the evolution of reproductive barriers that stop two different groups of organisms from breeding.

Types of reproductive barriers
Types of Reproductive Barriers they are

  • Some reproductive barriers stop individuals of different species form mating.

    • Different species may mate in different places, at different times, or after different mating courtship behaviors.

    • In other cases, individuals of different species will not mate because their sexual organs simply do not fit together.

Other reproductive barriers
Other reproductive barriers they are

  • A second type of reproductive barrier causes matings between different species to fail

  • The mating may not produce offspring, or may produce offspring that die or are sterile (unable to reproduce themselves)

    • Example – when a lion

      and tiger mate,

      a liger is produced.

      The liger is sterile.

Geographic barriers
Geographic barriers they are

  • Most common cause of speciation

  • A geographic barrier arises when two populations become physically separated. Can include mountain ranges, glaciers, rivers, oceans, canyons, or land (in the case of aquatic organisms.

  • Geographic barriers allow different populations to evolve independently and sometimes to evolve reproductive barriers.

  • If this happens, the different populations become separate species.

Evolutionary trees
Evolutionary trees they are

  • Evolutionary trees are diagrams that show how different species are related.

  • The divergent lines

    show when speciation


27 3 three domains of life
27.3 Three Domains of Life they are

  • Life is classified into three domains-

    • Bacteria

    • Archaea

    • Eukarya

  • Probably 2.5 – 3.5 billion years ago, living organisms split into two separate lineages – one that produced Bacteria and the other that produced Archaea and Eukarya

Domains they are

  • Bacteria and Archaea are prokaryotic organisms

  • Eukarya are eukaryotic organisms

    • Further divided into four kingdoms

    • Protists

    • Fungi

    • Plants

    • Animals

  • Check out main characteristics on pg 574.

27 4 bacteria
27.4 Bacteria they are

  • Live on your body by the millions, occupy habitats no other organism can survive and devastate human populations with diseases such a plague and tuberculosis.

  • Earth’s oldest fossils – 3.5 billion years old are of bacteria

  • Prokaryotes that are so diverse it is hard to make generalizations about them

Bacteria characteristics
Bacteria characteristics they are

  • Some make their own food through photosynthesis; Some obtain food from other organisms

  • Most are single-celled but others gather together in multicellular clusters

  • Come in different shapes- including spheres, rods and spirals

  • Many can move with flagella

  • Reproduce asexually by dividing (as often as every 20 minutes)

  • In poor conditions many can form spores (tough, thick-walled structures) that can survive for long periods of time until conditions improve.

More on bacteria
More on bacteria they are

  • Important role as decomposers- break down organic material; life on earth would be impossible without them

  • Important for humans- help with digestion, make vitamins that we can use; good bacteria keep bad bacteria away

  • Used to make foods such as yogurt and cheese

  • Help make human insulin and other medicines

  • Can also cause disease (tuberculosis, syphilis, Lyme) but antibiotics (substances that kill bacteria) have helped with this.

27 5 archaea
27.5 they areArchaea

  • Once considered a funny looking bacteria

  • Now considered to be a distinct group of prokaryotes that are more closely related to eukaryotes than prokaryotes.

  • Many live in extreme environments

  • This group is called ‘extremophiles’ because they can survive in extremely salty environments, very hot springs and hydrothermal vents.

More on archaea pronounced our kee uh
More on they areArchaea- pronounced our-kee-uh

  • Not all are extremists. Many live in the ocean.

  • Some are chemoautotrophs that make food using chemical energy rather than energy from sunlight.

  • Those that live in hydrothermal

    vents get energy from

    hydrogen sulfide- entirely

    independent of the sun.

27 6 protists
27.6 Protists they are

  • Eukaryotes that are not plants, fungus or animals are lumped together in a group called protists.

  • Include species that can photosynthesize as well as those that get their food form other organisms.

  • Some are single-celled, others are multicellular.

  • Many reproduce asexually, while others reproduce sexually.

  • Because there are so many different species that are just lumped together, scientists are in the process of splitting this group up.

Photosynthetic protists
Photosynthetic protists they are

Single-celled protists that float in the ocean.

Have elaborate shells made out of silica

Used in man-made products like toothpaste


Dinoflagellates they are

Singled-celled protists that live in the ocean.

When sunlight and nutrients are plentiful, they ‘bloom’ (reproduce rapidly) causing ‘red tides’ – ocean actually turns red because of the large amount of them

Some red tides are toxic

When shellfish eat the dinoflagellates, they become contaminated and poisonous to humans.

Multi cellular photosynthetic protists
Multi-cellular photosynthetic they areprotists

  • All seaweeds are protists.

  • Kelp is a protist that forms huge ocean forests.

Heterotrophic protists getting their food from other organisms
Heterotrophic they areProtists –getting their food from other organisms

  • Most are active, single-celled hunters

  • Amoebas move by extending part of their body forward and then pulling the rest behind- called cytoplasmic streaming

  • They eat by engulfing their prey

Other heterotrophic protists
Other heterotrophic protists they are

  • Ciliates – move by beating numerous hairlike projections called cilia

Flagellates- move by whipping a long flagellum

Diseases from protists
Diseases from protists they are

  • Malaria- protist divides its time between mosquitoes and humans

  • African sleeping sickness- protist divides time between tsetse fly and humans

  • Amoebic dysentery- Montezuma's revenge

27 8 fungi
27.8 Fungi they are

  • Because they don’t move, scientists used to put fungus with plants. But they are more closely related to animals than they are plants.

  • Like animals, they obtain their food from other organisms.

  • They obtain food by releasing digestive enzymes over organic matter and then absorbing the nutrients..

  • Animals digest their food inside their bodies- fungus digest their food outside their bodies.

More on fungi
More on fungi they are

  • Reproduce asexually or sexually

  • Reproduce by making spores- tiny reproductive bodies that can exist in a dormant state for long periods until conditions are good for growth.

  • Fungal spores spread through the air or water.

  • Examples of fungus: mushrooms, mold, mildew, yeast

  • Some Fungal diseases: yeast infections, ringworm, athlete's foot

  • Uses: yeast- baking, brewing; mushrooms- food; cheese making; antibiotics (penicillin) found in a fungus

27 7 plants
27.7 Plants they are

  • Multi-cellular organisms that can photosynthesize- use the energy from sunlight to make their own food and organic molecules.

  • They share many adaptations

    • Roots- anchor the plant to the ground and absorb water and nutrients from the soil

    • Shoots- stems and leaves of the plant- where photosynthesis occurs

    • Many have a vascular system- a plant ‘circulatory system’ that distributes water and other resources – called sap

Major groups of plants mosses ferns seed plants
Major Groups of Plants- mosses, ferns, seed plants they are


  • Small plants with no vascular system

  • Absorb water directly through the environment through diffusion

  • To reproduce, sperm

    have to swim through a film

    of water to the eggs

  • Have to live in moist

    habitats like bogs and

    shady forests

Ferns they are

  • Have a vascular system

  • Sperm must swim to eggs

  • Must live is moist environment

  • Have distinctive feathery leaves

Seed plants largest group
Seed Plants- largest group they are

  • Key to their success – pollen and seeds

  • Pollen- male reproductive cells wrapped in a protective coating

    • Can be transported to female reproductive structures by wind or by animals – don’t need to swim

  • Seed- a small plant embryo that is placed inside a tough outer covering with a supply of food

    • Can survive in a dormant state where no growth or development occurs until environmental conditions are good

Two main groups of seed plants conifers and flowering plants
Two main groups of seed plants- conifers and flowering plants

  • Conifers- redwoods, pines, cedars & firs

    • gymnosperms

  • Waxy, needle-like leaves

  • Reproductive structures called cones

    • Male cones produce pollen that is carried by the wind to female cones

    • Fertilization occurs in the female cones and seeds are eventually dropped form the female cones

Flowering plants angiosperms
Flowering Plants- angiosperms plants

  • Biggest and most successful group because they have flowers and fruit

  • Flowers function in reproduction- they contain male structures that make pollen and female structures that produce eggs

  • In many flowering plants, pollen is transported by insects or animals

  • Flower petals, scent and nectar have evolved to attract these polinators

fruit plants

  • Flowering plants surround their seeds with a structure called a fruit

  • Fruits help flowering plants spread their seeds around

  • Animals can eat the fruit and the seeds get dispersed through their digestive tracks

  • Or, the fruit can attach itself to the animal’s fur (burrs)

  • Allows the seeds to be moved far from the parent plant- helps ensure survival

Important: Fruit is the name for the seed covering of a flowering plant- it refers not to just our ’fruits’ but also many

of our vegetables

27 9 animals
27.9 Animals flowering plant- it refers not to just our ’fruits’ but also many

  • Multi-cellular organisms that obtain nutrients by eating other organisms. They usually take food into their bodies for digestion

  • Most animals also have muscles for moving, sense organs for making sense of their environments, and nervous systems for controlling their actions.

Major animal groups
Major Animal groups flowering plant- it refers not to just our ’fruits’ but also many

  • Sponges

  • Cnidarians

  • Flatworms

  • Roundworms

  • Arthropods

  • Mollusks

  • Annelids

  • Echinodrems

  • Chordates

Sponges flowering plant- it refers not to just our ’fruits’ but also many

  • Sedentary (nonmoving) animals that live in the ocean

  • Most have a tube-like shape with a large central cavity

  • Water enters the cavity through many pores carrying food with it and exits through the top

Cnidarians flowering plant- it refers not to just our ’fruits’ but also many

  • Animals such as jellyfish, sea anemones and corals

  • Catch prey using stinging tentacles

  • Many start their lives as polyps (sedentary) and grow into medusa that swim. Some (corals, sea anemones) spend their lives as polyps

Flatworms flowering plant- it refers not to just our ’fruits’ but also many

  • Long, ribbon-like worms

  • Many are parasites that live in or on organisms doing them harm

  • Best known flatworm- the tapeworm that lives as a parasite in humans and other animals

Roundworms flowering plant- it refers not to just our ’fruits’ but also many

  • Live either in the water or on land

  • Different from earthworms, they are very small (can be thousands in a handful of soil)

  • Slender bodies with muscles that run from head to tail

Arthropods flowering plant- it refers not to just our ’fruits’ but also many

  • All have an outer skeleton- exoskeleton- that protects and supports the organism

  • Exoskeleton doesn’t grow- it is shed repeatedly as the organism grows

  • Insects are the largest group of living organisms on the planet- more than a million known insect species

  • Important as plant pollinators; many can carry disease (West Nile virus, malaria, etc)

Huge group of animals that includes lobsters, barnacles, spiders, scorpions, ticks, centipedes, insects, and many other species

Found in every known habitat on earth

Mollusks flowering plant- it refers not to just our ’fruits’ but also many

  • Soft-bodied animals such as clams, oysters, squids, octopuses, snails, slugs

  • Most have a protective shell although the shell is tiny in some species (squid) and absent in some (octopus, slugs)

Annelids flowering plant- it refers not to just our ’fruits’ but also many

  • Worms such as earthworms and leeches

  • Bodies divided into segments

  • Earthworms-important decomposers

  • Leeches- parasites that eat blood of host

Echinoderms flowering plant- it refers not to just our ’fruits’ but also many

  • Starfish, sea urchins, sea cucumbers

  • Have small sucker-like tube feet that they use to move

  • Can use them to pry open shellfish

  • Move very, very slowly

Chordates flowering plant- it refers not to just our ’fruits’ but also many

  • Include vertebrates, the group to which humans belong

  • Vertebrates are animals with backbones- fish, amphibians, reptiles, mammals

Chordates groups of fish
Chordates- flowering plant- it refers not to just our ’fruits’ but also many groups of fish

  • Cartilaginous fish- sharks, rays, skates

    • Don’t have bones- skeletons made of cartilage

  • Ray-finned fish (bony fish)

    • what we think of as fish

    • Tuna, bass, salmon, etc.

    • Swim bladders allow them to maintain the same density as the water- they don’t sink or float- gives them great mobility

Chordates amphibians
Chordates- amphibians flowering plant- it refers not to just our ’fruits’ but also many

  • Live both on land and in the water

  • Include animals like salamanders and frogs

  • Can live only in moist environments or their skin dries out

  • Amphibian eggs have no shell and require moisture to develop

Chordates reptiles
Chordates- flowering plant- it refers not to just our ’fruits’ but also many reptiles

  • Includes turtles, lizards and snakes, crocodiles

  • All are ectoderms- what we used to call ‘cold-blooded’ they use behaviors to regulate their body temperature

  • All reptiles- skin made of dead cells (doesn’t dry out)

  • Eggs have shells (keeps them form drying out)

Chordates birds
Chordates- flowering plant- it refers not to just our ’fruits’ but also many birds

  • Birds have adaptations for flight – wings, feathers, hollow bones (lightweight)

  • Endoderms- keep a constant, high body temperature by breaking down large amounts of food- this process generates heat

Chordates mammals
Chordates- mammals flowering plant- it refers not to just our ’fruits’ but also many

  • Have hair and feed their young milk

  • All are endoderms

  • Most live on land, but bats fly and two groups, seals and whales are partly or fully aquatic

  • 3 major groups

    • Monotremes- (platypus) lay eggs

    • Marsupials – (possums, koalas, kangaroos)- give birth to immarture young that develop in a pouch

    • Placentals- give birth to more mature live young