Chapter 8 Visually Section 1 HOW POPULATIONS CHANGE IN SIZE Key Words: population, dense population, dispersed population, growth rate, exponential growth, carrying capacity

7. Define population. 8. If a population is to grow exponentially (very rapidly), organisms must have plenty of __________, ____________, and little or no ______________. 9. The fastest rate at which a population can grow is its ___________ potential. 10. List 5 things that can cause a population to decrease:____________ __________________________ ______________________ __________________________ ______________________ 11. In 1911, 25 reindeer were placed on Pribilof Island near Alaska. They ate primarily lichens, which are very slow growing. By 1938, the herd numbered almost 2,000. In 1950, there were only 8 deer on the island. What do you suppose happened? 12. Rabbits were introduced to Australia in There was plenty of vegetation, and their population rapidly increased. Twenty years later, hardly any were left? What do you think happened? 13. T/F Populations are in constant flux as individuals reproduce, die, or migrate in or out of a given area. 14. Change in population size = Births - _____________ MATCH THE FOLLOWING TERMS TO THE CORRECT PIC: Competition for food Competition for space Competition for dominance

Cp. 8 Review Which pic better describes a habitat for lions? Which better describes a lion’s niche? A B Interactions Between Species Label each picture:

Competition Predation Parasitism Mutualism Commensalism

Even humans are occasionally infected with parasites such as tapeworms, round worms, mosquitoes and leeches. Parasitism is a biological relationship in which one species benefits; while harming the other and can occur in the smallest biolgoical niche. Because the parasite needs the host to remain alive, it is typically advantageous for the parasite NOT to kill its host, however there are examples of when death of the host occurs. In photo B, a tomato hornworm is covered with cocoons of pupating braconid wasps. The braconid wasp is considered a parasitoid of the hornworm because it causes the hornworm to die as it pupates. By the time the wasps undergo metamorphosis, all of the hosts insides have been digested, thus by the time they are ready to pupate, the caterpillar will die. While this may be detrimental to the tomato hornworm, it is considered beneficial for gardeners...as the tomato hornworm can be a signifant pest. Parasitism usually connotes a negative feeling; however as seen in this case, it can be considered beneficial. Commensalism is a relationship between two species where one species derives a benefit from the relationship and the second species is unaffected by it. Several examples of commensalism are: The anemonefish lives among the forest of tentacles of an anemone and is protected from potential predators not immune to the sting of the anemone. The anemonefish is protected from the sting of the anomone tentacles by a substance contained in the mucous on its skin. The exact nature of this protective substance is not known, but is believed to be a combination of a partial natural secretion and chemicals the fish harvests by rubbing up against the anemone's tentacles. What ever the case may be, the anemone treats the fish as part of itself and does not sting it. INTERACTIONSpecies ASpecies BDescription CompetitionHarmedEach negatively affects the other PredationBenefited MutualismBenefitedEach helps the other. CommensalismBenefitedA benefits but B is unaffected ParasitismBenefited

Even humans are occasionally infected with parasites such as tapeworms, round worms, mosquitoes and leeches. Parasitism is a biological relationship in which one species benefits; while harming the other and can occur in the smallest biological niche. Because the parasite needs the host to remain alive, it is typically advantageous for the parasite NOT to kill its host, however there are examples of when death of the host occurs. In photo B, a tomato hornworm is covered with cocoons of pupating braconid wasps. The braconid wasp is considered a parasite of the hornworm because it causes the hornworm to die as it pupates. By the time the wasps undergo metamorphosis, all of the hosts insides have been digested, thus by the time they are ready to pupate, the caterpillar dies. While this may be detrimental to the tomato hornworm, it is considered beneficial for gardeners...as the tomato hornworm can be a significant pest. Parasitism usually connotes a negative feeling; however as seen in this case, it can be considered beneficial to gardeners.

Commensalism is a relationship between two species where one species derives a benefit from the relationship and the second species is unaffected by it. An example of commensalism: The anemonefish (clown fish) lives among the forest of tentacles of sea anemones and is protected from potential predators not immune to the sting of the anemones. The clownfish is protected from the sting of the anemone tentacles by a substance contained in the mucous on its skin. The exact nature of this protective substance is not known, but is believed to be a combination of a partial natural secretion and chemicals the fish harvests by rubbing up against the sea anemone's tentacles. What ever the case may be, the anemone treats the clown fish as part of itself and does not sting it.

The Cattle Egret (Bubulcus ibis) forages in pastures and fields among livestock such as cattle and horses, feeding on the insects stirred up by the movement of the grazing animals. Egrets benefit from the arrangement, but the livestock, generally, do not. However, as in most cases of commensalism, there is a “but”. Cattle Egrets have been observed perching on the backs of cattle, picking off ticks, and lending a tinge of mutualism to the interaction of the two species. (Not all relationships are purely one or the other!) Zooxanthellae produce food for their coral host in the form of simple sugar molecules that are formed in photosynthesis. They produce enough for themselves and enough to provide over eighty percent of the food requirements for many tropical reef building corals. Without the Zooxanthellae, coral would starve. Without the coral, zooxanthellae could be survive in the ocean.

When coyotes and badgers team up, the pairs track small, burrowing animals such as prairie dogs and ground squirrels. If the prey is above ground, the coyote usually chases it down, and the badger takes over the hunt if the prey descends underground. And not only do they find food together, but coyotes also have more success in this partnership than if they go it alone. Coyotes with badger cohorts catch an estimated one-third more ground squirrels than do solo coyotes! It all boils down to energy saving: badgers and coyotes conserve energy by sharing the workload of trapping elusive and fast-moving prey. Likewise, each animal takes advantage of the other’s hunting adaptations. Coyotes have keener eyesight for spotting prey than badgers. On the other had, badgers can sniff out prey underground. When the badger is busy digging for a squirrel, the coyote stalks around on top. The squirrel is forced to flee his burrow, and the coyote is ready to pounce! Sometimes the squirrel tries to flee the coyote, and is caught by the badger. Sometimes the coyote catches the squirrel. The relationship provides more prey for both species than either could find when working alone!