Biology and Society: Does Biodiversity Matter? – The expanding human population threatens


Biology and Society:

Does Biodiversity Matter?

– The expanding human population threatens

• Biodiversity

• The loss of natural ecosystems

© 2010 Pearson Education, Inc.


– Biological diversity, or biodiversity , includes

• Genetic diversity

• Species diversity

• Ecosystem diversity

Genetic Diversity

– The genetic diversity within populations of a species is the raw material that makes microevolution and adaptation to the environment possible.

– Genetic resources for that species are lost if

• Local populations are lost

• The number of individuals in a species declines

– Cultivated wheat is an example of a species with limited diversity, now threatened with the emergence of a parasitic fungus.

Species Diversity

– Ecologists believe that we are pushing species toward extinction at an alarming rate.

– The present rate of species loss

• May be 1,000 times higher than at any time in the past 100,000 years

• May result in the loss of half of all living plant and animal species by the end of this century

A Chinese river dolphin Golden toads

These species are now extinct.

Ecosystem Diversity

– The local extinction of one species can have a negative effect on the entire ecosystem.

– The loss of ecosystems risks the loss of ecosystem services , including

• Air and water purification

• Climate regulation

• Erosion control

–Coral reefs are rich in species diversity, yet

•An estimated 20% of the world’s coral reefs have been destroyed by human activities

•24% are in imminent danger of collapse

Causes of Declining Biodiversity

– Ecologists have identified four main factors responsible for the loss of biodiversity:

• Habitat destruction and fragmentation

• Invasive species

• Overexploitation

• Pollution

Habitat Destruction

– Biodiversity is threatened by the destruction and fragmentation of habitats by

• Agriculture

• Urban development

• Forestry

• Mining

Invasive Species

– Invasive species have

• Competed with native species

• Preyed upon native species

• Parasitized native species http://www.invasivespeci wa.shtml#thr

Scotch broom


– People have overexploited wildlife by harvesting at rates that exceed the ability of populations to rebound.

– Excessive harvesting has greatly affected populations of

• Tigers

• Whales

• The American bison

• Galápagos tortoises

• Tuna

• Etc…..


– Acid precipitation is a threat to

• Forest ecosystems

• Aquatic ecosystems

– Aquatic ecosystems may be polluted by toxic

• Chemicals

• Nutrients

A forest killed by acid rain


Important to understand to be able to stop its decline

The Evolution of Biological Novelty

• “What Darwin Never Knew”:

Evidence that LARGE biological changes can be brought about through small changes during embryonic development.

• Examples: limbs, thumbs, big brains

This can help to generate new species through evolutionary processes!

1.78 million species catalogued to date!

• Estimates range from 5-30 million species on Earth.

– From the Convention on Biological


• How do we keep track of them all?????

Classifying and Naming Species:


– Each species is assigned a two-part name or binomial , consisting of:

• The genus

• A name unique for each species

– The scientific name for humans is Homo sapiens (also H. sapiens ), a two part name, italicized and latinized, and with the first letter of the genus capitalized.

Hierarchical Classification

– Species that are closely related are placed into the same genus.

Leopard (Panthera pardus)

Tiger (Panthera


Lion (Panthera leo)

Jaguar (Panthera onca)

– The taxonomic hierarchy extends to progressively broader categories of classification


Panthera pardus




(Panthera pardus)

Dumb Kids Play

Chess On Full

G uy’s Stomach













Taxonomy had a problem…

What testable criteria do we use to classify species?

The Cladistic Revolution

– Cladistics is the scientific search for clades.

– A clade :

• Consists of an ancestral species and all its descendants that share a set of evolutionarily novel characteristics.

• Forms a distinct branch in the tree of life

– This is what Neil Shubin did in your extra credit reading selection from his book “Your Inner Fish”


Human Family Tree from Shubin’s “Your Inner Fish” (2009)

Cladistics in action

Humans are multicellular animals, that have a bilateral body plan, skulls, hands and feet, threeboned middle ears, a bipedal gait and large brains.

Another example of cladistics…


Duck-billed platypus

Kangaroo Hair, mammary glands


Long gestation






Figure 14.23

Let’s use cladistics to look at the evolutionary relationships of the immense biological diversity found on Earth

All organisms are made out of cells;

From your Flow of Matter model, all cells have a plasma membrane,

DNA, and ribosomes; all cells are made out of amino acids, nucleotides, fatty acids and glycerol, and monosaccharides!

Many metabolic processes evolved here.

Adaptation to an environment filled with oxygen evolved.

Figure 15.10

All organisms made out of eukaryotic cells

The Evolution of Eukaryotic Cells

The Endosymbiotic Model

The Diversity of Protists

Protozoans ingest food Slime molds digest food extracellularly

A malarial parasite!

Unicellular algae: photosynthetic

Multicellular algae: photosynthetic


Eukaryotic multicellular autotrophic (make their own food through photosynthesis) organisms adapted to live on land

Comparing evolutionary adaptations:

Living in water vs

Living on land

Highlights of Plant Evolution

– The fossil record chronicles four major periods of plant evolution.



Seedless vascular plants


Get out Lab 08: Take 5 min to read and share with class major adaptations of each.

Team A - Bryophytes

Team B - Seedless vascular plants

Team C - Gymnosperms

Team D - Angiosperms

Angiosperm life cycle

In the rest of Lab 08, we’ll discover the many adaptations for spreading seeds

Figure 16.19


Eukaryotic unicellular and multicellular heterotrophic

(rely on organic material for food) organisms that digest food externally and absorb nutrients


– Fungi are extremely important to ecosystems because they decompose and recycle organic materials.


• Eukaryotic, multicellular, heterotrophic organisms that obtain nutrients by ingestion.

• Digest their food within their bodies.

Animal Phylogeny

– To reconstruct the evolutionary history of animal phyla, researchers must depend on clues from the fossil record, comparative anatomy, embryology, and molecular biology.

– The first branch point is defined by the presence of true tissues.


Lacks true tissues

– The second major evolutionary split is based partly on body symmetry.

Cnidarians - true tissues and radial symmetry

– Phylum Cnidaria

• Is characterized by the presence of body tissues, radial symmetry, and tentacles with stinging cells.

Thimble jellies - cause disorder called Seabather’s eruption




Flatworms - bilateral symmetry

– Phylum Platyhelminthes

• Is represented by the simplest bilateral animals.

• Includes free-living forms such as planarians and parasitic forms such the tapeworm.

– Third, the evolution of body cavities led to more complex animals.

– A body cavity

• Is a fluid-filled space separating the digestive tract from the outer body wall.

• May be a pseudocoelom or a true coelom.


– Roundworms exhibit two innovations not found in flatworms:

• A complete digestive tract with two openings, a mouth and an anus

• A body cavity, which in this case is a pseudocoelom


– Phylum Annelida

• Includes worms with body segmentation.

• Have a true coelom


Check these out on your own!

Giant octopus attacks submarine


Cool mollusc movie! Scroll down

1/3rd way down


Purple clam opens


Arthropod Diversity

– There are four main groups of arthropods:

• Arachnids , such as spiders, scorpions, ticks, and mites

• Crustaceans , such as crabs, lobsters, crayfish, shrimps, and barnacles

• Millipedes and centipedes

• Insects , most of which have a three-part body


– Phylum Echinodermata

• Is named for the spiny surfaces of the organisms.

• Includes sea stars, sand dollars, sea urchins, and sea cucumbers.

Animal Phylogeny

– To reconstruct the evolutionary history of animal phyla, researchers must depend on clues from the fossil record, comparative anatomy, embryology, and molecular biology.

– Review your reading guide and the LONG version of lecture for a quick summary

Humans belong to this phylum

Characteristics of Chordates

– Members of the phylum Chordata all share four key features:

• A dorsal, hollow nerve cord

• A notochord

• Pharyngeal slits

• A post-anal tail

– An overview of chordate and vertebrate evolution

The Vertebrate Genealogy

– Vertebrates

• Are represented by mammals, reptiles, amphibians, and fishes.

• Have unique features, including the cranium and backbone.

– An overview of chordate and vertebrate evolution


– Tetrapods have 4 (tetra) limbs (pods).

– Includes amphibians, reptiles, and mammals

– Shows up in


• Exhibit a mixture of aquatic and terrestrial adaptations.

• Usually need water to reproduce.

– An overview of chordate and vertebrate evolution


• Amniotes adapted fluid-filled egg (in waterproof shell or carried by mother) for living on land.

• Includes reptiles and mammals

• Reptiles (including birds!) and some mammals lay amniotic eggs in which the embryo develops.

– An overview of chordate and vertebrate evolution

Getting closer to humans…


– Two features are mammalian hallmarks:

• Hair

• Mammary glands that produce milk and nourish the young

3 groups of mammals:

Primates are eutherian

(placental) mammals

The Human Ancestry

Humans are primates

Some Common Misconceptions

– Our ancestors were not chimpanzees or any other modern apes.

– Chimpanzees and humans represent two divergent branches of the anthropoid tree.

Common ancestor of chimps and humans; now extinct

– Human evolution

• Is not a ladder with a series of steps leading directly to Homo sapiens .

• Is more like a multi-branched bush than a ladder.

– Upright posture and an enlarged brain appeared at separate times during human evolution.

– Fossil evidence pushes bipedalism in A. afarensis back to at least 4 million years ago.

The Genus Homo and the

Evolution of Inventive Minds

– Homo habilis ,


• Had a larger brain.

• Probably made stone tools.

– Homo erectus

• Was taller than H. habilis .

• Had a larger brain.

• Gave rise to


The Origin and Dispersal of

Homo Sapiens

– The oldest known fossils of our own species, H. sapiens ,

• Were discovered in Ethiopia.

• Date from 160,000 to 195,000 years ago.

– Fossil evidence suggests that our species emerged from Africa in one or more waves,

• Spreading first into Asia and then to Europe and Australia.

Human Family Tree from Shubin’s “Your Inner Fish” (2009)

Cladistics in action

Humans are eukaryotic multicellular animals, that have a bilateral body plan, skulls

(vertebrates), hands and feet

(tetrapods), three-boned middle ears

(mammals), a bipedal gait and large brains.