All we have yet discovered is but a trifle in comparison with what lies hid in the great treasury of nature.

Antoine Van Leeuwenhoek

Biodiversity and Evolution

Unit 4

Case Study: Why Should We Protect Sharks?

• More than 400 known species.• 6 deaths/yr.• 79-97 million sharks killed every year: -Fins, organs, meat, hides, fear, by-catch• 32% shark species threatened with extinction.• Reasons for protection: cancer resistant, keystone species.

4-1 Importance of Biodiversity

• Biodiversity: the variety of Earth’s species, their genes, the ecosystems where they live, and the sustaining ecosystem processes (nutrient cycling, energy flow).

• Vital to sustaining life on earth (supplies us with food, wood, fiber, energy, and medicine).

Components of Biodiversity (cont’d)

• Functional diversity: bio/chemical processes needed for survival of species & communities.

-energy flow & matter recycling.• Ecosystem diversity: variety of terrestrial and

aquatic ecosystems. -storehouse of genetic, species diversity.

Components of Biodiversity

Species diversity: • Est. 8 million to 100 million species.• 1.9 million identified. -insects make up most of known species. -unidentified are mostly in rain forests and

oceans.Genetic diversity: variety of genetic material within a

population. -enables life to adapt to environmental changes.

FYI: Why You Should Love InsectsBad rep: compete for food, spread disease, bite

and sting, invade lawns.Natural capital: • pollination (allows flowering plants reproduce

sexually).• free pest control: insects eat other insects.

E.O. Wilson: Biodiversity

• Loved bugs as a kid.• Specialized in ants.• Widened scope to • earth’s biodiversity.• Theory of island biogeography.• First to use “biodiversity”

in a scientific paper.

4-2 Evolution of Species

Biological evolution: change in the genetic makeup of a species over generations.

Theory of evolution: organisms with adaptive traits have an advantage over others.

• Alfred Russell Wallace• Charles Darwin: -studied beak shape in Galapagos finches. -published On the Origin of Species by Means of

Natural Selection.

Natural Selection

Individuals with advantageous traits are more likely to survive & transmit traits to succeeding generations.

Steps of Selection

1. Genetic variability exists in a population. -mutations (random changes to DNA) are source of

variation. -mutations within gametes are inheritable.2. Environmental factors favor survival of individuals

with adaptive trait over others.3. Adaptive trait may lead to differential reproduction,

which enables individuals with adaptation to produce more offspring.

Natural Selection and the Six Kingdoms/Tree of Life

The Geologic Time Scale

Natural Selection & Genetic Resistance

• Ability of members of a population to resist a chemical designed to kill it.

Evidence of Natural Selection

• Fossil record: entire collection of preserved species.

-represents ≈ 1% of all species on Earth.

• Homologous structures: -similar structures in

dissimilar species.• DNA analysis

Limitations to Natural Selection

• Genetic change must precede change in the environmental conditions.

• Reproductive capacity: -Species that reproduce rapidly and in large

numbers are better able to adapt.

Common Myths about Evolution through Natural Selection

• “Survival of the fittest” is not “survival of the strongest” .

(Fittest is in terms of leaving behind the most offspring )

• Organisms do not develop traits out of need or want.

• No grand plan of nature for perfect adaptation (evolution is not “goal oriented).

Case Study: How Did Humans Become Such a Powerful Species?

Three human adaptations:• Strong opposable thumbs• Walk upright• Complex brain: allows for weapon development, creation of protective devices,

and technologies that extend our senses.

4-3 Geology and Natural Selection

• Tectonic plates affect evolution and the location of life on earth.

-change the location of continents & oceans. -influences climate & distribution of species. -species became geographically isolated from

one another. • Earthquakes: shifting of tectonic plates; may

isolate populations.• Volcanic eruptions: occur near plate boundaries;

may wipe out populations.

Movement of the Earth’s Continents over Millions of Years

Pangea’s breakup explained: Scrat’s Missing AdventureVideo Clip , Video Clip 2

Climate Change and Natural Selection

• Cyclical climate changes restrict location/ survival of populations.

-adapt, migrate or become extinct

Catastrophes and Natural Selection

• Collisions between the Earth & large asteroids have occurred throughout history. -caused destruction of ecosystems/species. -created opportunities for new species.

4-4 Biodiversity, Speciation and Extinction

• Biodiversity results from the interaction between speciation and extinction.

Extinction

• Biological extinction: effects global population.• Local extinction: widespread, but not global.• Endemic species: found only in one area; particularly

vulnerable to extinction.• Background extinction: typical low rate of extinction. -1-5 species per million species/year.• Mass extinction: above background rate. -3-5 over 500 million years.

Golden Toad of Costa Rica

Climatic change, pollution, ultraviolet radiation, and/or fungal skin infections? No one knows why it went extinct.

Found in cloud forests 2000 m above sea level.

Fig. 4-12, p. 93

Tertiary

Bar width represents relative number of living speciesEra Period

Species and families experiencing

mass extinctionMillions ofyears ago

Ordovician: 50% of animal families, including many trilobites.

Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites.

500

345

Cambrian

Ordovician

Silurian

Devonian

Extinction

Extinction

Pale

ozoi

cM

esoz

oic

Ceno

zoic

Triassic: 35% of animal families, including many reptiles and marine mollusks.

Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites.

Carboniferous

Permian

Current extinction crisis causedby human activities. Many speciesare expected to become extinctwithin the next 50–100 years.

Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including manyforaminiferans and mollusks.

Extinction

Extinction

Triassic

Jurassic

Cretaceous

250

180

65Extinction

ExtinctionQuaternary Today

Mass Extinctions

FYIThe Passenger Pigeon - Gone Forever

• Once the most numerous bird on earth.

• In 1858, Passenger Pigeon hunting became a big business.

• By 1900 they became extinct from over-harvest and habitat loss.

Figure 11-1

Global Extinction

• Some animals have become prematurely extinct because of human activities.

Figure 11-2

Fig. 11-3, p. 224

Hawksbill sea turtle

Giant panda Black-footed ferret

Whooping crane

Northern spotted owl

Blue whale

Mountain gorilla Florida panther

California condor

Black rhinoceros

Speciation

Evolutionary process by which new biological

species arise:• Geographic isolation: physical isolation of

populations for a long period lead to…• Reproductive isolation: mutations in

geographically isolated populations prevent the production of viable offspring.

Geographic Isolation Can Lead to Reproductive Isolation

Changing Genetic Traits

• Genetic engineering: alters genes by adding, deleting segments of DNA for desired trait(s).

• Artificial selection: useselective/crossbreeding

Normal mouse (left) vs. Transgenic mouse with Human Growth Hormone

4-5 The Importance of Species Diversity

• Species richness: number of different species in a given area.

• Species evenness: the comparative number of individuals of each species in an ecosystem.

-low evenness: few individuals of each species.

-high evenness: many individuals of each species.

FYI: Species Richness and EvennessWhich plot has a higher species richness? Each color represents a different species.

Which plot has a greater species evenness?

Variations in Species Richness and Species Evenness

High species richness Low species richnessLow species evenness High species evenness

Species Richness on Islands

• Species equilibrium model, theory of island biogeography. • Rate of new species immigrating should balance

with the rate of species extinction• Island size and distance from the mainland need

to be considered. -small islands have a higher extinction rates. -islands closest to the mainland have greater

species richness.

Effects of Species Richness

• Determined by two factors: -plant productivity (more plant biomass) -enhanced sustainabilityFYI: Current hypothesis suggests that the more species, the more nutrients, the more pathways for energy flow. Our buddy, E O Wilson says,“There’s a common sense to this: the more species you have, the more likely you’re going to have an insurance policy for the whole ecosystem”.

4-6 Roles of Species in an Ecosystem

• Ecological niche: role of species & everything needed for its survival.

Generalists

Generalist species: broad niches• many different

locations• varied diet• tolerate wide range of

conditions

Specialists

Specialist species:narrow niches• restricted habitat• restricted diet• narrow tolerance of

environmental conditions

Five Major Species Roles in Ecosystems

1. Native: normal resident.2. Nonnative: migrate, introduced into. -AKA invasive, alien, exotic3. Indicator: provide early warnings of damage to communities.4. Keystone: role determines types, abundance of other species in community.5. Foundation: create, enhance habitats for other species.

Invasive Species

Fig. 11-11a, p. 234

Deliberately Introduced Species

Purple loosestrife European starling African honeybee(“Killer bee”)

Nutria Salt cedar(Tamarisk)

European wild boar(Feral pig)

Marine toad(Giant toad)

Water hyacinth Japanese beetle Hydrilla

FYI: Invasive Species• The Argentina fire

ant was introduced to Mobile, Alabama in 1932 from South America.– Most probably from

ships.– No natural

predators.

Figure 11-12

Indicator Species

Keystone Species

Foundation Species

Exam Focus

• Role of shark/top predator in ecosystem.• Components of biodiversity• Link between biodiversity, speciation & extinction.• Most abundant identified species.• Steps of natural selection, including the “raw”

material that drives it and its result.• Basics of geologic time scale/resulting kingdoms.• Role of plate tectonics in speciation

Exam Focus (cont’d)

• Genetic resistance.• Importance of fossil record to evolution.• Reasons for vulnerability to extinction of

endemic and specialist species.• Sequence of order in speciation (geo or repro).• Species richness vs evenness.• Ecological niche

Exam Focus

• Traits of generalists vs specialists.• 5 species roles and examples.• Expect questions from previous units.