Anna Dornhaus

Assistant Professor in the Ecology & Evolutionary

Biology Department

University of Arizona

How everything in nature is connected

“Ecology” is the study of how organisms interact with their environment

Ecology

• What they eat

• Where & when they live

• Who eats them

Interacting with your environment

Ecology

Interacting with your environment

Ecology

Interacting with your environment

Ecology

Interacting with your environment

Ecology

Food chain

Food chain

Interacting with your environment

Predator

Prey

Food chain

Interacting with your environment

Predator

Consumer

Producer

Food chain

• Every food chain starts with a producer

• Trophic level: high trophic levels are far from producers

Interacting with your environment

Predator

Consumer

Producer

How does the producer produce?

Cycles of matter

Predator

Consumer

Producer ?

How does the producer produce?

Cycles of matter

• Producers: plants, algae, and some bacteria

• The process of creating organic matter (sugars, proteins, etc.) from inorganic matter (salts, water, air) in plants is called photosynthesis.

Making plants

Cycles of matter

• Light is the energy that drives this process

• Carbon dioxide (or CO2) from the air and water from the soil are used to make sugars

• Oxygen is a waste product

Cycles of matter

Predator

Consumer

Producer

CO2 + water

Producers make organic

material; others just process it

Who eats the predator?

Cycles of matter

Predator

Consumer

Producer

CO2 + water

?

Cycles of matter

Predator

Consumer

Producer

CO2 + water

Decomposer

Cycles of matter

Predator

Consumer

Producer

CO2 + water

Decomposer

Cycles of matter

Predator

Consumer

Producer

CO2 + water

Decomposer

10%

10%

10%

Cycles of matter

Predator

Producer

10%

1%

This means that predators ultimately only use 1% of the

original plant-produced biomass.

To feed people meat, you need 10x more

plants (area) than to feed people grains

Food chain

Interacting with your environment

Predator

Prey

Interacting with your environment

Interacting with your environment

Food web

Ecological networks

Seed dispersersPlants

Interacting with your environment

… but in reality with thousands of species

and many more interactions

Interactions

Organisms also interact in other ways than eating or being eaten. For example:

Other interactions

• Competition for food or nesting sites• Parasitism• Mutualism:

– Pollination– Seed dispersal– etc.

Interactions

PollinationWhat is pollination?

Interactions

PollinationWhat is pollination?

• Plants having sex without moving!

• Pollinators collecting food

Interactions

PollinationWhat is pollination?

• Plants having sex without moving!

• Pollinators collecting food

Plants offer nectar to attract animals (bees, bats, moths, other insects); in collecting nectar, these animals get pollen stuck on them, which is transported to the next plant

Interactions

Pollination

Interactions

PollinationWhy do plants produce

colorful, nice-smelling flowers?

Interactions

PollinationWhy do plants produce

colorful, nice-smelling flowers?

To attract pollinators! (and thus get their sperm=pollen spread to other plants!)

Interactions

Seed dispersalWhy do plants produce

colorful, sugary fruits?

Interactions

Seed dispersalWhy do plants produce

colorful, sugary fruits?

To attract seed-dispersers!

(often birds)

Interactions

Plants need animals!Many plants cannot survive unless the right pollinators and the right seed disperser are present.

Interactions

Protection:Ants and barrel cacti

Cactus offers nectar, ants protect cactus by killing caterpillars and other herbivores

Interactions

Protection: Ants and acacias

Bullhorn acacia tree, Pseudomyrmex ant

Interactions

MutualismsMutualistic interaction between different species evolved many times and is widespread.

• Humans and livestock• Humans and gut bacteria• Mushrooms and trees• Orchids and fungus• Mitos and chloroplasts in cells• Ants and plants with extrafloral

nectaries (e.g. barrel cacti)

• Ants and aphids• Leaf-cutting ants and

fungus• Clownfish and sea

anemones• Corals and zooxanthellae

Interactions

Close association of individuals of different species:

Usually involves exchange of chemicals that one of the partners cannot make alone.

Symbioses

Lichens – a symbiosis of a fungus and a bacterium

The abiotic environment

Why are most cacti only found in the American deserts?

The abiotic environment

Why does any organism live where it lives?

Usually three kinds of explanations:

• Abiotic environment (the right climate, nesting sites, etc.)

• Biotic interactions (prey is there)

• History (it evolved there and did not migrate somewhere else)

The abiotic environment

Why are most cacti only found in the American deserts?

• Abiotic environment (dry with periodic rain; not too cold)

• Biotic interactions (can defend themselves against desert herbivores and compete with other desert plants)

• History (evolved in the Americas, and cannot migrate to Africa, for example)

Organisms interact with their biotic and abiotic environment

Each animal & plant • is part of a food web• has a ‘trophic level’ (producer or consumer)• interacts with other organisms in other ways

(parasitism, competition, mutualisms)• requires a certain abiotic environment (climate

etc. – more on this later)

Producers can make organic matter from inorganic; all others have to eat organic matter

Summary: ecology

• PBS Evolution series: The evolutionary arms race: chapter 7 "Symbiosis and leafcutter ants" (12 minutes)