Chapter 13: Life in the Ocean Insert: Textbook cover photo

Main Concepts All of Earth’s life-forms are related. All have apparently evolved from a single ancient instant of origin. Evolution happens. Organisms change as time passes, adapting by natural selection to their environments. Oceanic life is classified by evolutionary heritage. All life activity is involved, directly or indirectly, in energy transformation and transfer. Primary productivity involves the synthesis of organic materials from inorganic substances by photosynthesis or chemosynthesis. Primary productivity is expressed in grams of carbon bound into organic material per square meter of ocean surface area per year (gC/m2/yr). The atoms and small molecules that make up the biochemicals, and thus the bodies, of organisms move between the living and nonliving realms in biogeochemical cycles. An organism’s success can be limited by inappropriate amounts of these materials and the physical and biological conditions surrounding the organism. The success of marine organisms depends on their relation with the physical and biological factors that influence them. Rapid change may result in mass extinction.

Life on Earth Is Notable for Its Unity and Its Diversity Life on Earth exhibits unity and diversity: diversity because Earth may house as many as 100 million different species (kinds) of living organisms; unity because all species share the same underlying mechanisms for capturing and storing energy, manufacturing proteins, and transmitting information between generations. In a sense, all life on Earth is fundamentally the same - it’s just packaged in thousands of different ways. Earth’s organisms have changed, or evolved, over more than 4 billion years.

Evolution Appears to Operate by Natural Selection Evolution occurs through the process of natural selection. In any group of organisms, more offspring are produced than can survive to reproductive age. Random variations occur in all organisms. Some of these traits are inheritable. Some inheritable traits make an organism better suited to its environment (most do not). Because bearers of favorable traits are more likely to survive, they are also more likely to reproduce successfully than bearers of unfavorable traits. The physical and biological (natural) environment itself does the selection.

Evolution Appears to Operate by Natural Selection Evolution by natural selection is the accumulation of beneficial inheritable traits, known as adaptations. A species is a group of actually (or potentially) interbreeding organisms that is reproductively isolated from all other forms of living things. Because conditions in the open ocean are relatively uniform, large marine animals with similar lifestyles but different evolutionary heritages eventually tend to look much the same. This is known as convergent evolution.

Systems of Classification May Be Artificial or Natural The study of biological classification is called taxonomy. (RIGHT) Carolus Linnaeus invented three supreme categories, or kingdoms: animal, vegetable, and mineral. Today’s biologists leave the mineral kingdom to the geologists and have expanded Linnaeus’s two living kingdoms to six. Linnaeus’s great contribution was a system of classification based on hierarchy, a grouping of objects by degrees of complexity, grade, or class.

Systems of Classification May Be Artificial or Natural A family tree showing the relationship of the three domains that presumably evolved from a distant common ancestor. The Bacteria and Archaea contain single-celled organisms without nuclei or organelles; collectively, they are called prokaryotes. The fungi, protists, animals, and plants contain organisms with cells having nuclei and organelles; collectively, they are called eukaryotes.

Systems of Classification May Be Artificial or Natural The modern system of biological classification, using the California gull (Larus californicus) as an example. Note the boxes-within-boxes approach, a hierarchy.

The Flow of Energy Allows Living Things to Maintain Complex Organization What distinguishes life from non-life is the ability of living things to capture, store, and transmit energy - and the ability to reproduce. Energy can be stored by photosynthesis or chemosynthesis. Photosynthesis is the process used by most producers to convert the sun’s energy to food energy. Chemosynthesis is the production of food from inorganic molecules in the environment.

The Flow of Energy Allows Living Things to Maintain Complex Organization A comparison of photosynthesis and chemosynthesis

The Flow of Energy Allows Living Things to Maintain Complex Organization The flow of energy through living systems. At each step, energy is degraded (that is, transformed into a less useful form).

Primary Producers Synthesis Organic Materials The synthesis of organic materials from inorganic substances by photosynthesis or chemosynthesis is called primary productivity. Phytoplankton are responsible for producing between 90% and 96% of the surface ocean’s carbohydrates. Seaweeds contribute from 2% to 5% of the ocean’s primary productivity. Chemosynthetic organisms probably account for between 2% and 5% of the total productivity in the water column.

Global Primary Productivity Oceanic productivity can be observed from space. NASA’s SeaWiFS satellite can detect the amount of chlorophyll in ocean surface water. Chlorophyll content allows an estimate of productivity. Red, yellow, and green areas indicate high primary productivity; blue areas indicate low.

Food Webs Disperse Energy through Communities Autotrophs – organisms that make their own food, also called producers. Heterotrophs – organisms that must consume other organisms for energy Trophic pyramid – a model that describes who eats whom Primary consumers – these organisms eat producers Secondary consumers – these organisms eat primary consumers Top consumers – the top of the tropic pyramid

Food Webs Disperse Energy through Communities A generalized trophic pyramid. How many kilograms of primary producers is required for an average tuna sandwich? Using the trophic pyramid model shown here, you can see that 1 kilogram of tuna (enough to make ten 1/4-pound tuna sandwiches) at the fifth trophic level (the fifth feeding step of the pyramid) is supported by 10,000 kilograms of phytoplankton at the first level.

Food Webs Disperse Energy through Communities Diatoms, and other primary producers, convert the energy from the sun into food used by the rest of the oceanic community. A simplified food web, illustrating the major trophic relationships leading to an adult blue whale.

Living Organisms Are Built from a Few Elements The atoms and small molecules that make up the biochemicals, and thus the bodies, of organisms move between the living and nonliving realms in biogeochemical cycles. Carbon - present in all organic molecules Nitrogen - found in proteins and nucleic acids Phosphorus and silicon – found in rigid parts of organisms Iron and trace metals - used for electron transport

The Carbon Cycle Is Earth’s Largest Cycle Because of its ability to form long chains to which other atoms can attach, carbon is considered the basic building block of all life on Earth.

Nitrogen Must Be “Fixed” to Be Available to Organisms The Nitrogen Cycle. The atmosphere’s vast reserve of nitrogen cannot be assimilated by living organisms until it is “fixed” by bacteria and cyanobacteria, into a biologically available form. Nitrogen is an essential element in the construction of proteins, nucleic acids, and a few other critical biochemicals.

Physical and Biological Factors Affect the Functions of an Organism A limiting factor is a factor found in the environment that can be harmful if present in quantities that are too large or too small. Any factor required for life can become a limiting factor. Any aspect of the physical environment that affects living organisms is a physical factor. The most important physical factors for marine organisms: Light, dissolved gases, temperature, salinity Acid-base balance, hydrostatic pressure, nutrients

Physical and Biological Factors Affect the Functions of an Organism Biological factors also affect living organisms in the ocean. Some biologic factors that affect ocean organisms: Feeding relationships Crowding (competition for space) Metabolic wastes Defense of territory

Environmental Factors Influence the Success of Marine Organisms The depth to which light penetrates is limited by the number and characteristics of particles in the water. The upper, sunlit zone of the ocean is known as the photic zone. In the euphotic zone, there is enough light for photosynthesis. Below that depth, in the disphotic zone, light may be present, but not enough to produce net glucose. The aphotic zone lies in permanent darkness.

Temperature Influences Metabolic Rate The ocean temperature varies with depth and latitude. The rate at which chemical reactions occur in an organism is largely dependent on heat. (LEFT) Temperatures of marine waters capable of supporting life. Some areas of the ocean, such as hydrothermal vents, may support specialized living organisms at temperatures of up to 400°C (750°F)!

Substances Move through Cells by Diffusion, Osmosis, and Active Transport Marine organisms rely on these processes for many functions. Diffusion is mixing due to random molecular movements. Osmosis is diffusion of water through a membrane. Active transport is the transport of a substance against a concentration gradient. Active transport requires energy input. (LEFT) The effects of osmosis in different environments. (a) An isotonic solution. Cells placed in isotonic solutions do not change size since there is no net movement of water. (b) A hypertonic solution. A cell placed in a hypotonic solution will shrink. (c) A hypotonic solution. A cell placed in a hypotonic solution will swell.

The Marine Environment Is Classified into Distinct Zones Scientists divide the marine environment into zones, areas with homogeneous physical features. Zones are classified by location and the behavior of the organisms found there.