Diversity and Interdependence of

Life

Speciation• We have learned that evolution is the process of

DNA mutations creating new species over time.• What determines if different organisms are

different species? What is a species?

A species consists of all individuals that can breed together and produce fertile offspring.

This definition is called the Biological Species Concept.

A female donkey mated to a male horseproduces what?

A mule (which is sterile)Hence, donkeys and horses are separate species.

Criticisms of the Biological Species Concept• Cannot be used with asexual organisms (bacteria).• Cannot tell if fossil specimens were capable of

interbreeding.• Doesn’t account for isolation:

– Behavioral isolation: having different courtship rituals or behaviors

– Geographic isolation: separated by geographic barriers

– Temporal isolation: reproduce at different times

How are different species named?• Taxonomy- The science of naming and classifying

organisms.

• A Swedish biologist named Carolus Linnaus came up with a two-word system for naming organisms. It is called binomial nomenclature.

• There are 7 levels of classification:Kingdom-Phylum-Class-Order-Family-Genus-Species

• In binomial nomenclature, the first word is the organism’s genus name and the second word is the species name.

Human ClassificationKingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Primate

Family: Hominidae

Genus: Homo

Species: Sapien (means “wise”)

•Using binomial nomenclature, we are Homo sapiens. Always capitalize the genus and italicize or underline both the genus and species names.

The levels get more specific as you work down to the species.

Have all living things been classified?

• NO! Our knowledge of all living things is limited.

• Classification is based on anatomy, embryology, DNA, behavior, and when the organism evolved.

• If you are unsure of the binomial nomenclature of an organism, you can use an identification system called a dichotomous key.

Example of a Dichotomous Key

Interdependence of Life• Ecology- The study of relationships

between living things and their environment.

• Biosphere- The area around the earth where life exists.– includes the hydrosphere, lithosphere, and

atmosphere

Levels of the Biosphere• Biome- a large area characterized by certain animal

and plant species as well as climate• Ecosystem- All of the living and non-living

components of a particular geographic area.• Community- A naturally occurring group of plants and

animals living in a particular area.• Population- A group of organisms of one type

(species) living in a particular area.• Habitat- The physical area in which an organism lives.• Climate- The prevailing weather conditions of a

geographic area.

Levels of a Biosphere

BIOSPHERE

ECOSYSTEM

COMMUNITY

BIOME

POPULATION

NON-LIVING COMPONENT (Habitat and Climate)

• Abiotic- Non-living Components– Sunlight– Temperature– Soil– Soil chemistry– Precipitation– Rocks– Erosion

• Biotic – Living Components– Plants– Animals– Fungus– Bacteria– Protists

Components of an Ecosystem

Where do viruses belong?

Trophic Levels of EcosystemsA trophic level is a

“feeding level”.– The relationship

between what an organism eats and what eats it.

– Where it fits into a food chain/web

– The 1st Trophic Level is at the bottom of the food chain.

How Biotic Factors Obtain EnergyProducer (Autotroph)

• Organisms that can make their own food = organic (carbon containing) materials

• At the 1st Trophic Level

• Examples: plants and bacteria

• Photosynthetic- Use energy from sunlight and convert it into organic energy

• Chemosynthetic- Use energy from inorganic compounds and covert it into organic energy

Consumer (Heterotroph)Organisms that cannot make their own food and must get it from an external source.•Primary (1st) consumer- herbivore- eats only producers•Secondary (2nd) consumer- carnivore- eats only consumers

• Tertiary (3rd), quaternary (4th), etc.

•Omnivore- eats producers and consumers•Detritivore- breaks down wastes and dead bodies•Decomposer- fungi, bacteria: return nutrients to the soil for absorption

Food Chain• Food Chain: Specific feeding sequence in which

organisms obtain energy in an ecosystem

Grass Caterpillar Sparrow Snake Coyote

Arrows always point in the direction of energy flow!

• Food Web: Interrelated food chains

FOOD WEB :• What is/are the producer(s)?• What is a herbivore?• What is a primary consumer?• What is a secondary consumer?• What is a tertiary consumer?• What would be 3 consequences in the fish population died out?

How do we keep track of energy in ecosystems?

• Ecological Pyramids- A diagram that shows the amounts of energy at each trophic level in a food chain or food web. (3 types)

1. Numbers Pyramid: counts the # of individuals (does not discriminate by size) – can be an inaccurate indicator of energy at that level

– Ex. Caterpillars outnumber the trees that they feed on

2. Biomass Pyramid: measures amount of living tissue (dry weight) in grams

3. Energy Pyramid: measures amount of energy stored in tissues (ex. fats = 9 Cal/gram;

carbohydrates/proteins = 4 Cal/gram)

Numbers Pyramid

Biomass Pyramid

Energy Pyramid

Energy Transfer• Amount of energy available to do work

decreases as energy passes through a system• 10% transfer of energy (90% energy lost) from

one level to the next. Most is lost to the air as heat.

• How much energy would be transferred to each level of the following food chain?

GrassCaterpillarSparrow Snake Coyote1200 kcal ? ? ? ?

Population Size• Studying changes in population size is

called population ecology.

• This helps scientists predict future changes in populations and better understand how to conserve biodiversity.

• Counting members of a population is often impossible. Estimation of population size can calculated using the Capture-Recapture Method.

Capture-Recapture Method• In the Capture-Recapture Method, a sample of

animals are caught and tagged. They are then released back into their habitat. Other samples are then captured at various times and each time the total number and marked number of animals are noted.

• The following equation is then used to estimate population size. N= # originally marked x total # animals captured

# of animals marked that were captured

20 fish were captured, marked and put back into a pond. On 10 different occasions, samples were taken from the pond. What is the estimated population size?

# obtained in the sample # marked in the sample

15 2

12 4

18 0

22 2

12 1

16 1

13 3

11 4

16 2

20 2

How do populations grow?

• Most populations grow either exponentially or logistically.

• Exponential growth occurs when resources are plentiful and the reproduction rate is greater than the death rate.

• On a graph, exponential growth looks like a “J”.

How do populations grow? • Logistic growth occurs if there are limited

resources and growth of the population begins to slow as competition for those resources increases. The growth of the population eventually slows to nearly zero as the population reaches the carrying capacity for the environment.

• On a graph, logistic growth looks like a “S”.