1. Chapter 12: Interactions Within Ecosystems
12.1: Groups of living things interact within ecosystems
12.2: Organisms can interact in different ways
12.3: Ecosystems are always changing

2. Review An ecosystem is composed of only biotic factors
Both biotic and abiotic
In a species, the organisms’ offspring must be able to breed
True
The same niche in a habitat may be occupied by more than one species
Different species never occupy exactly the same niche

3. Organisms interact in different ways
Competition, cooperation
Organisms sharing a habitat, and resources within that habitat
Different relationships between organisms exist and determine how they interact
Ex: robin pulls an earthworm from soil
One eats, the other gets eaten
Ex: Robin vs chickadee – compete for earthworm
Ex: Ants work together to build a nest, collect food, and defend the colony

4. Predator and Prey Involving food
Food chain interaction: relationship between producers and consumers
Predator and prey interaction, also seen in the food chain
Predators: impact distribution of prey population
Herrings move in a school, and wildebeests travel in herds
To protect themselves
Sick and elderly are most susceptible to predation
Cicadas: 17 yr reproductive cycle is beneficial because predator population remains generally low
Prey: impact distribution of predator population
Birds preying on insects: bird population is dependant on insect population

5. The hare population is kept in check by predation by lynx, and the lynx depended entirely on hares for food

6. Competition In a biological community, to win…is to survive
Struggle between individuals or different populations for a limited resource
Competition may be within the same species, or between species
Plants competing for light, space, and nutrients
Creosote bushes: toxins produced by roots
Strangler figs (vines) compete with trees for water, light and nutrients
Attaches itself to host tree, grows and vines surround and eventually kill the tree

7. Competition Vultures and hyenas compete over scavenging a dead animal
Wolves compete over territory by urinating on trees
Other animals compete by fighting and threatening sounds
Often occurs during mating season
Male birds sing or display feathers to compete for female attention
Male hippopotamuses fight for attention
Male crickets chirp
Coexistence is possible
Many species living together in the same habitat without causing harm to one another
(food)
(living space)
(a mate)

8. Cooperation
“An interaction in which organisms work in a way that benefits them all”
Lions may hunt in packs to kill large prey
Killer whales swim in packs called pods
circle a school of fish – easier to catch
Take turns chasing a seal until it tires
Ants, bees, termites are social insects
Different groups (castes) with different responsibilities within a community
Some gather food, others defend the colony
Apes, monkeys, live in family groups
Care for young

9. Bees
Cooperation
Termites

10. Survival of one species might depend on another species
The fact that organisms live together forces them to interact in different ways
Predator/prey
Competition for food/water/territory
Some are so closely related that the survival of one species depends on another
At least one of the species is getting food, reproductive help, or protection, etc
Symbiosis: ”living together”
Both species benefit from the relationship
One species benefits while the other is not affected
One species benefits while the other is harmed

11. Both Species Benefit Mutualism
flowers and bees – the bees get food (nectar) and the flowers get pollination) to make new seeds)
Other plants are similar: insects that feed on the nectar transfer pollen from one flower to the next
Seeds are then moved to the ground by animals that eat the seeds or the fruits that hold the seeds
Doesn’t benefit the individual flower, but ensures survival of the species
Termites: feed on wood, but need the tiny protozoans in their gut to break down the wood
Both Species Benefit

12. Mutualism Ex: Lichen
Layer of fungi on the outside with a filling of an algal species on the inside
The fungus species attaches the lichen structure to the log, rock, or brick wall it lives on and absorbs nutrients from the environment
In addition the fungus forms a protective envelope for the algae preventing the algae from drying out.
The algae in its turn uses the nutrients absorbed by the fungus and the carbon dioxide produced to photosynthesize
The sugars and oxygens produced by the algae are, in turn, used for food by the fungus
This allows lichens to colonize habitats that are hardly survivable by other plant and animal species

13. One Species Benefits Commensalism:
Orchids and mosses have a commensal relationship with trees
They grow on the trunks or branches
Get enough light and nutrients that run down the tree
If they don’t grow too heavy they cause no harm to the tree
Ocean ecosystems
Remoras use a suction cup to stick to a shark’s skin for the ride
Feed on the shark’s killing scraps
The shark is barely affected

14. One Species Benefits
Some fish protect themselves by swimming within the stinging tentacles of a moon jellyfish
Keeps the fish safe from predators
It is common in commensal relationships for the species that benefits to be smaller than the partner

15. One Species is Harmed
Parasitism – often tiny organisms that feed off, and weaken, its hosts
External: ticks, lice, mites
Internal: tapeworms, ringworms
Female cowbirds lay eggs in warbler nests
Warbler eggs do not hatch or chicks do not survive (cowbird chicks are larger)

16. Life on the Coral Reef Cooperation and Symbiosis.asf
Changes within communities.asf
Types of Interactions Between Ecosystems.asf

17. Evolutionary Arms Race
explores the connection between an organism's behavioral and physical traits and its environment
interactions among different types of organisms and the importance of these relationships to the evolution of species
Part I: Life-Changing Relationships
Animal defense:
Masters of disguise
Toxic newts:
Ancient farmers of the Amazon:
Part II: Exploring Interactions on the Great Barrier Reef