Review Unit 7 Exam

Chapter 34 •

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What environmental factors determine the geographic distribution of gray whales? How do variations in their food supply affect the size of the gray whale population? These questions are the subject of ecology, the scientific study of the interactions between organisms and their environment. o These interactions occur on a hierarchy of scales from organismal to global, including abiotic factors.

Abiotic factors affect the distribution of organisms. •

Sunlight provides the energy that drives nearly all ecosystems. o

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Light intensity is not the most important factor limiting plant growth in most terrestrial environments, although shading by a forest canopy creates intense competition for light in the understory.

The variation in water availability among habitats is an important factor in species distribution. o

Intertidal species may face desiccation as the tide recedes.

Abiotic factors are the major components of climate. • Four abiotic factors—temperature, water, sunlight, and wind—are the major components of climate. • Climatic factors, especially temperature and water, have a major influence on the distribution of organisms and their homeostasis. o Wind has a the greatest direct effect on an organism’s water loss by evaporation. Species dispersal contributes to the distribution of organisms.

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The movement of individuals away from centers of high population density or from their area of origin is called dispersal. o

Perhaps there are no kangaroos in North America due to barriers to their dispersal.

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Adaptations to their current environment may be deleterious in another environment.

The structure and distribution of terrestrial biomes are controlled by climate and disturbance

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Tropical forests are found close to the equator and have the greatest amount of input and least seasonal variation in solar radiation. oTropical rain forests receive constant high amounts of rainfall (200–400 cm annually), thus determining the type of the kind of vegetation. o In tropical dry forests, precipitation is seasonal. oIn both rain and dry forests, air temperatures range between 25°C and 29°C year-round. oTropical forests are stratified, and competition for light is intense. oThere is more animal diversity in tropical forests than in any other terrestrial biome. oWith distinct wet and dry seasons, tropical deciduous trees and shrubs are common.

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Savanna is found in equatorial and subequatorial regions. oRainfall is seasonal, averaging 30–50 cm per year. oThe savanna is warm year-round, averaging 24–29°C with some seasonal variation. oSavanna vegetation is grassland with scattered trees. oLarge herbivorous mammals are common inhabitants. oThe dominant herbivores are insects, especially termites.

oFire is important in maintaining savanna biomes.

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Deserts occur in a band near 30° north and south latitudes and in the interior of continents. oDeserts have low and highly variable rainfall, generally less than 30 cm per year. oTemperature varies greatly both seasonally and daily. oDesert vegetation is usually sparse and includes succulents, such as cacti, and deeply rooted shrubs. oMany desert animals are nocturnal, so they can avoid the heat. oDesert organisms display adaptations that allow them to resist or survive desiccation.

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Chaparrals have annual precipitation ranging from 30 to 50 cm, with mild, wet winters and dry, hot summers. oChaparral is dominated by shrubs and small trees, with a diversity of grasses and herbs. oPlant and animal diversity is high. oAdaptations to fire and drought are common. oThis type of ecosystem is found in both the central valley of central and southern California and the Mediterranean area.

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Temperate grasslands exhibit seasonal drought, occasional fires, and seasonal variation in temperature. oLarge grazers and burrowing mammals are native to temperate grasslands. oDeep fertile soils make temperate grasslands ideal for agriculture, especially for growing grain. oMost grassland in North America and Eurasia has been converted to farmland, because it is the best agricultural land. oSeasonal drought and frequent fires, contribute to perpetuate temperate grasslands, such as the American prairies, and prevent them from becoming woodlands

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Coniferous forest, or taiga, is the largest terrestrial biome on Earth. oConiferous forests have long, cold winters and short, wet summers. oThe conifers that inhabit these forests are adapted for snow and periodic drought. oConiferous forests are home to many birds and mammals. oThese forests are being logged intensively, and old-growth stands of conifers may soon disappear.

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Tundra covers large areas of the Arctic, up to 20% of Earth’s land surface. oAlpine tundra is found on high mountaintops at all latitudes, including the tropics. oThe plant communities in alpine and Arctic tundra are very similar. oThe Artic tundra winter is long and cold, while the summer is short and mild. The growing season is very short. oTundra vegetation is mostly herbaceous, consisting of a mixture of lichens, mosses, grasses, forbs, and dwarf shrubs and trees. oA permanently frozen layer of permafrost prevents water infiltration and restricts root growth.  Permafrost is also, fundamentally responsible for the character of arctic tundra soils oLarge grazing musk oxen are resident in Arctic tundra, whereas caribou and reindeer are migratory. oMigratory birds use Arctic tundra extensively during the summer as nesting grounds. oArctic tundra is sparsely settled by humans but has recently become the site of significant mineral and oil extraction. Aquatic biomes are diverse and dynamic systems that cover most of Earth

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Light is absorbed by the water and by photosynthetic organisms, so light intensity decreases rapidly with depth.

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There is sufficient light for photosynthesis in the upper photic zone.

The substrate at the bottom of an aquatic biome is the benthic zone.

oThe benthic zone is made up of sand and sediments and is occupied by communities of organisms called

benthos. oA major food source for benthos is dead organic material or detritus, which “rains” down from the productive surface waters of the photic zone.

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Estuaries are areas of transition between river and sea – fresh and seawater meet.

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The marine benthic zone consists of the seafloor below the surface waters of the coastal or neritic zone and the offshore pelagic zone, where a sperm whale may be found in the Atlantic Ocean. oMost of the ocean’s benthic zone receives no sunlight. oOrganisms in the very deep abyssal zone are adapted to continuous cold (about 3°C) and extremely high pressure. oUnique assemblages of organisms are associated with deep-sea hydrothermal vents of volcanic origin on midocean ridges. oThe primary producers in these communities are chemoautotrophic prokaryotes that obtain energy by oxidizing H2S formed by a reaction of volcanically heated water with dissolved sulfate (SO42−)

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Human influence on the ecosystems The use of agricultural fertilizer, even if free of pesticides, is often harmful to temperate lakes o The runoff causes a surface algal bloom, which reduces the lake's oxygen by cutting off the sunlight and fouling the water with dead organic matter. The major reason for tropical deforestation is people clearing forests to open up land for agriculture. Chapter 35

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Social behavior is broadly defined as interaction between two or more animals

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Human social behavior appears to be a product of our genes, external influences, and environment. A discrete sensory input is the stimulus for a wide range of animal behaviors.

Classical ethology presaged an evolutionary approach to behavioral biology • Proximate questions, directed towards immediate mechanisms of “how” a behavior occurs. Signals function in animal communication. • The transmission and reception of signals constitute animal communication. • Communication may occur through the various senses. o The organism’s surroundings will the determine the specific method of signaling.  A nocturnal animal, will communicate preferably by using small and sound. •

Honeybees use a symbolic language to share information about the location of food sources. oThe language was discovered in the 1940s by ethologist Karl von Frisch, who studied the behavior of the European honeybee (Apis mellifera carnica).

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A bee returning from a foraging trip is the center of attention for other follower bees. o If the food source is close to the hive (less than 50 m away), the returning bee displays a “round dance,” moving in tight circles while waggling its abdomen from side to side. o When a source of food is farther from the nest, the returning bee performs a “waggle dance”, consisting of a half-circle swing in one direction, a straight run, and a half-circle swing in the other direction to communicate the direction and distance of the food source from the hive.

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Learning establishes specific links between experience and behavior Behavior that is developmentally fixed in this way is called innate behavior. o This includes a newborn’s suckling after a nipple being placed in his mouth.

Animals may use cognitive maps to navigate efficiently within their surroundings. • In place of landmark orientation, some animals guide their activity by a cognitive map, a neural representation of the spatial relationships between objects in an animal’s surroundings. o The most extensive studies of cognitive maps has been done with migrating animals. Selection for individual survival and reproductive success can explain most behaviors. Mating systems and extent of parental care vary greatly.

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Mating behavior, which includes seeking and attracting mates, choosing among potential mates, and competing for mates, is the product of a form of natural selection called sexual selection.

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How mating behavior enhances reproductive success varies, depending on the species’ mating system.

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The mating relationship between males and females varies a great deal from species to species. oIn many species, mating is promiscuous, with no strong pair-bonds or lasting relationships. oIn species in which the mates remain together for a longer period, the relationship may be monogamous (one male mating with one female) or polygamous (one individual mating with several partners). oPolygamous relationships may involve a single male and many females (polygyny) or a single female and many males (polyandry).

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Hormone levels have an effect on the organism’s sexual behavior. o

Endocrine disruptors may affect sexual behavior by mimicking a hormone or enhancing hormonal activity.

Selection for individual survival and reproductive success can explain most behaviors. •

A territory is usually determined for feeding.

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The pecking order observed in chickens can be determined by dominance hierarchy.

Inclusive fitness can account for the evolution of altruistic social behavior.

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Altruism is behavior that decreases individual fitness but increases the fitness of other individuals in the population. o

From a sociobiological point of view, altruism may have the potential to enhance the altruist's fitness at a later point in time.

Chapter 36: Dynamic biological processes influence population density, dispersion, and demographics.

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A population is a group of individuals of a single species that live in the same general area.

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A graphic way of representing the data in a life table is a survivorship curve, a plot of the numbers or proportion of individuals in a cohort of 1,000 individuals still alive at each age. Ecologists define carrying capacity (K) as the maximum stable population size that a particular environment can support. oCarrying capacity is not fixed but varies over space and time with the abundance of limiting resources.

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Some populations show cyclic population changes – these cycles are also called “boom-and-bust” cycling. oSmall herbivorous mammals such as voles and lemmings tend to have 3- to 4-year cycles. oRuffled grouse and ptarmigan have 9- to 11-year cycles.

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Selection for life history traits that maximize reproductive success at low densities is known as r-selection, or density-independent selection. or-selection tends to maximize r, the per capita rate of increase, and occurs in environments in which population densities fluctuate well below K or when individuals face little competition.  Such conditions are often found in disturbed habitats.

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Age structure, the relative number of individuals of each age, is illustrated as a pyramid showing the percentage of the population at each age, and future growth.

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To maintain population stability, a regional human population can exist in one of two configurations: Zero population growth = High birth rates − High death rates Zero population growth = Low birth rates − Low death rates

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The movement from the first toward the second state is called the demographic transition.

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Population ecologists predict a population of 7.8–10.8 billion people on Earth by 2050.

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The concept of an ecological footprint summarizes the aggregate land and water area appropriated by each person, city, or nation to produce all the resources it consumes and to absorb all the waste it generates. oIf the area of all the ecologically productive land on Earth is divided by the global human population, the result is about 2 hectares (ha) per person. oReserving some land for parks and conservation means reducing this allotment to 1.7 ha per person—the benchmark for comparing actual ecological footprints. oAnyone who consumes resources that require more than 1.7 ha to produce is using an unsustainable share of Earth’s resources. oA typical ecological footprint for a person in the United States is about 10 ha.