Biodiversity, Species Interaction, and Population Control Chapter 5 pgs. 100-108 Biodiversity, Species Interaction, and Population Control

Chapter Overview Questions What determines the number of species in a community? How can we classify species according to their roles in a community? How do species interact with one another? How do communities respond to changes in environmental conditions? Does high species biodiversity increase the stability and sustainability of a community?

Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? They were over-hunted to the brink of extinction by the early 1900’s and are now making a comeback.

Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? Sea otters are an important keystone species for sea urchins and other kelp-eating organisms.

COMMUNITY STRUCTURE AND SPECIES DIVERSITY Biological communities differ in their structure and physical appearance. Figure 7-2

Tropical rain forest Coniferous forest Deciduous forest Thorn forest Figure 7.2 Natural capital: generalized types, relative sizes, and stratification of plant species in various terrestrial communities. Tropical rain forest Coniferous forest Deciduous forest Thorn forest Thorn scrub Tall-grass prairie Short-grass prairie Desert scrub Fig. 7-2, p. 144

Case Study: Why are Amphibians Vanishing? Frogs serve as indicator species because different parts of their life cycles can be easily disturbed. Figure 7-3

Adult frog (3 years) Young frog Sperm Tadpole develops into frog Sexual Reproduction Tadpole Figure 7.3 Typical life cycle of a frog. Populations of various frog species can decline because of the effects of harmful factors at different points in their life cycle. Such factors include habitat loss, drought, pollution, increased ultraviolet radiation, parasitism, disease, overhunting for food (frog legs), and nonnative predators and competitors. Eggs Fertilized egg development Egg hatches Organ formation Fig. 7-3, p. 147

Case Study: Why are Amphibians Vanishing? Habitat loss and fragmentation. Prolonged drought. Pollution. Increases in ultraviolet radiation. Parasites. Viral and Fungal diseases. Overhunting. Natural immigration or deliberate introduction of nonnative predators and competitors.

SPECIES INTERACTIONS: COMPETITION AND PREDATION Species can interact through competition, predation, parasitism, mutualism, and commensalism. Some species evolve adaptations that allow them to reduce or avoid competition for resources with other species (resource partitioning).

Resource Partitioning Each species minimizes competition with the others for food by spending at least half its feeding time in a distinct portion of the spruce tree and by consuming somewhat different insect species. Figure 7-7

Niche Specialization Niches become separated to avoid competition for resources. Figure 7-6

Region of niche overlap Number of individuals Species 1 Species 2 Region of niche overlap Resource use Figure 7.6 Natural capital: resource partitioning and niche specialization as a result of competition between two species. The top diagram shows the overlapping niches of two competing species. The bottom diagram shows that through natural selection the niches of the two species become separated and more specialized (narrower) so they avoid competing for the same resources. Number of individuals Species 1 Species 2 Resource use Fig. 7-6, p. 150

SPECIES INTERACTIONS: COMPETITION AND PREDATION Species called predators feed on other species called prey. Organisms use their senses their senses to locate objects and prey and to attract pollinators and mates. Some predators are fast enough to catch their prey, some hide and lie in wait, and some inject chemicals to paralyze their prey.

PREDATION Some prey escape their predators or have outer protection, some are camouflaged, and some use chemicals to repel predators. Figure 7-8

(a) Span worm Fig. 7-8a, p. 153 Figure 7.8 Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior. (a) Span worm Fig. 7-8a, p. 153

(b) Wandering leaf insect Figure 7.8 Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior. (b) Wandering leaf insect Fig. 7-8b, p. 153

(c) Bombardier beetle Fig. 7-8c, p. 153 Figure 7.8 Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior. (c) Bombardier beetle Fig. 7-8c, p. 153

(d) Foul-tasting monarch butterfly Figure 7.8 Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior. (d) Foul-tasting monarch butterfly Fig. 7-8d, p. 153

(e) Poison dart frog Fig. 7-8e, p. 153 Figure 7.8 Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior. (e) Poison dart frog Fig. 7-8e, p. 153

(f) Viceroy butterfly mimics monarch butterfly Figure 7.8 Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior. (f) Viceroy butterfly mimics monarch butterfly Fig. 7-8f, p. 153

(g) Hind wings of Io moth resemble eyes of a much larger animal. Figure 7.8 Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior. (g) Hind wings of Io moth resemble eyes of a much larger animal. Fig. 7-8g, p. 153

Figure 7.8 Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior. (h) When touched, snake caterpillar changes shape to look like head of snake. Fig. 7-8h, p. 153

SPECIES INTERACTIONS: PARASITISM, MUTUALISM, AND COMMENSALIM Parasitism occurs when one species feeds on part of another organism. In mutualism, two species interact in a way that benefits both. Commensalism is an interaction that benefits one species but has little, if any, effect on the other species.

Parasites: Sponging Off of Others Although parasites can harm their hosts, they can promote community biodiversity. Some parasites live in host (micororganisms, tapeworms). Some parasites live outside host (fleas, ticks, mistletoe plants, sea lampreys). Some have little contact with host (dump-nesting birds like cowbirds, some duck species)

Mutualism: Win-Win Relationship Two species can interact in ways that benefit both of them. Figure 7-9

(a) Oxpeckers and black rhinoceros Figure 7.9 Natural capital: examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plant growth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi. (a) Oxpeckers and black rhinoceros Fig. 7-9a, p. 154

(b) Clownfish and sea anemone Figure 7.9 Natural capital: examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plant growth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi. (b) Clownfish and sea anemone Fig. 7-9b, p. 154

(c) Mycorrhizal fungi on juniper seedlings in normal soil Figure 7.9 Natural capital: examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plant growth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi. (c) Mycorrhizal fungi on juniper seedlings in normal soil Fig. 7-9c, p. 154

(d) Lack of mycorrhizal fungi on juniper seedlings in sterilized soil Figure 7.9 Natural capital: examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plant growth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi. (d) Lack of mycorrhizal fungi on juniper seedlings in sterilized soil Fig. 7-9d, p. 154

Commensalism: Using without Harming Some species interact in a way that helps one species but has little or no effect on the other. Figure 7-10

ECOLOGICAL SUCCESSION: COMMUNITIES IN TRANSITION New environmental conditions allow one group of species in a community to replace other groups. Ecological succession: the gradual change in species composition of a given area Primary succession: the gradual establishment of biotic communities in lifeless areas where there is no soil or sediment. Secondary succession: series of communities develop in places containing soil or sediment.

Primary Succession: Starting from Scratch Primary succession begins with an essentially lifeless are where there is no soil in a terrestrial ecosystem Figure 7-11

Lichens and mosses Exposed rocks Balsam fir, paper birch, and white spruce forest community Figure 7.11 Natural capital: primary ecological succession over several hundred years of plant communities on bare rock exposed by a retreating glacier on Isle Royale, Michigan (USA) in northern Lake Superior. The details vary from one site to another. Jack pine, black spruce, and aspen Heath mat Small herbs and shrubs Time Fig. 7-11, p. 156

Secondary Succession: Starting Over with Some Help Secondary succession begins in an area where the natural community has been disturbed. Figure 7-12

Time Mature oak-hickory forest Young pine forest with developing Figure 7.12 Natural capital: natural ecological restoration of disturbed land. Secondary ecological succession of plant communities on an abandoned farm field in North Carolina (USA). It took 150–200 years after the farmland was abandoned for the area to become covered with a mature oak and hickory forest. A new disturbance such as deforestation or fire would create conditions favoring pioneer species such as annual weeds. In the absence of new disturbances, secondary succession would recur over time, but not necessarily in the same sequence shown here. Young pine forest with developing understory of oak and hickory trees Shrubs and pine seedlings Perennial weeds and grasses Annual weeds Time Fig. 7-12, p. 157

Can We Predict the Path of Succession, and is Nature in Balance? The course of succession cannot be precisely predicted. Previously thought that a stable climax community will always be achieved. Succession involves species competing for enough light, nutrients and space which will influence it’s trajectory.

ECOLOGICAL STABILITY AND SUSTAINABILITY Living systems maintain some degree of stability through constant change in response to environmental conditions through: Inertia (persistence): the ability of a living system to resist being disturbed or altered. Constancy: the ability of a living system to keep its numbers within the limits imposed by available resources. Resilience: the ability of a living system to bounce back and repair damage after (a not too drastic) disturbance.

ECOLOGICAL STABILITY AND SUSTAINABILITY Having many different species appears to increase the sustainability of many communities. Human activities are disrupting ecosystem services that support and sustain all life and all economies.