Biology: The Study of Life

“Bio”- living, life

“Logos”- knowledge/study

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Human Impact: Humans are members of the Biosphere

Biosphere

Entire portion of planet where life occurs

from the upper atmosphere to ocean floor and below

Ecosystem

Consists of all the organisms living in a particular area (plants, animals, bacteria) as well as all the nonliving, physical components of the environment with which the organisms interact (air, soil, water, sunlight)

Ex: marsh, forest, mountain lake, desert 3

Organization of the Biosphere

Many types of ecosystem

Tundra

Tropical rainforests

Deserts

Kelp forests

Coral reefs4

Organization of the Biosphere

Major determinant of which ecosystem is found where is climate

Deserts = low rainfall

Tropical rainforests = wet & warm

Coral reefs = shallow, clear warm oceans

Reefs and tropical rainforests are both homes to wide diversity of organisms

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Within an Ecosystem:Community: All living organisms in an ecosystem

Organisms in communities interact with one another and are often strongly dependent upon one another (form food webs, etc)

Population: All members of same species which may mate with one another within an area

Many populations in one community

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Ecosystems are dynamic environments

Organisms exchange materials and energy with their environment

Energy and nutrients are cycled through

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Ecosystems are characterized by:

Cycling of materials

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How do humans impact this?

Ecosystems are characterized by:

Flow of energy

Food chains

Food webs

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How do humans impact this?

Human PopulationHuman activities shape ecosystems

cut down forests

plow grasslands

drain marshes

build houses and roads

Redirect water

Activities often result in pollution that changes ecosystems

Effects are particularly bad in rainforest and coral reefs

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Human PopulationHuman activities have

Destroyed > 10% of coral reefs and damaged another 30%

Cut down rainforests

Polluted water

Harming ability of world’s ecosystems to support us, our children and other species

Just starting to realize how strongly we depend on our ecosystems

We may be changing our planet in unforeseen, negative ways 11

BiodiversityBiodiversity = number of species, and their genetic variability

Between 2 and 20 million species alive today

Human activities threaten many of them

Hundreds of species go extinct every day

Many more have been reduced to a very small number of individuals

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BiodiversityEach individual has only two sets of chromosomes

Each can carry only 2 copies of the gene for any trait

Fewer individuals = less genetic diversity

Natural selection acts on diversity

If individuals don’t have needed traits to survive in environment, all will die

Fewer genetic options = more likely extinction is as environment changes

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Biodiversity

Loss of species and loss of genetic diversity in today’s ecosystems is worrying

Are human activities leading to a “mass extinction” like the one 65 million years ago when the dinosaurs all died?

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