SAM GIRLS COLLEGE, BHOPAL

SAM GIRLS COLLEGE, BHOPAL
DEPARTMENT OF LIFE SCIENCES

Presented by Ms. Razda Asst. Proff. Life Science Department
FOOD CHAIN Presented by Ms. Razda Asst. Proff. Life Science Department

Energy Flow and Energy Loss in Ecosystems: Food Chains
Scientists use different methods to represent energy moving through ecosystems. Food chains Food webs Food pyramids

FOOD CHAIN The foods are synthesized by producers are utilized by primary consumers. The primary consumers are eaten by secondary consumers & in turn they are consumed by tertiary consumers which are utilized by decomposers. In this way a chain is formed by consuming food of different trophic levels, sequentially which is called FOOD CHAIN.

The transfer of energy from sun to producer to primary consumer to secondary consumer to tertiary consumer can be shown in a FOOD CHAIN.

TYPES OF FOOD CHAIN GRAZING FOOD CHAIN – Begins from green plants & proceeds towards herbivores & then towards carnivores. DETRITUS FOOD CHAIN- starts from rotten organic substances & proceeds towards carnivores through detrivores. Food Webs Remember that food chains are an artificiality that don't really exist. In reality, the trophic linkages between organisms are much more complicated. Most organisms have more than one predator and the diets of animals shift as they develop. Food webs reflect the complexity of trophic interactions.

FOOD CHAINS Food chain that includes the following organisms:
CONSUMER (CARNIVORE) Food chain that includes the following organisms: grasshopper mouse grass owl CONSUMER (CARNIVORE) CONSUMER (HERBIVORE) PRODUCER

Examples of terrestrial and aquatic food chains

FOOD CHAINS A food chain shows the path of energy from one organism to the next energy flows from producers to consumers arrows point to who is eating (plant is eaten by herbivore) Usually decomposers are left out

FOOD WEBS In an ecosystem, numerous food chain are interrelated to each other & form a food web. A food web shows all feeding relationships in an ecosystem (made of many food chains)

Food Webs: Are interconnected food chains
They show the feeding relationships in an ecosystem

Diamondback rattlesnake
Red-tailed hawk Producer to primary consumer Gambel's quail Primary to secondary consumer Yucca Agave Jack rabbit Collared lizard Secondary to higher-level consumer Prickly pear cactus All producers and consumers to decomposers Roadrunner Diamondback rattlesnake Darkling beetle Bacteria Fungi Kangaroo rat

Food Webs Food chains don’t exist in real ecosystems
Almost all organisms are eaten by more than one predator Food webs reflect these multiple and shifting interactions Food Webs Remember that food chains are an artificiality that don't really exist. In reality, the trophic linkages between organisms are much more complicated. Most organisms have more than one predator and the diets of animals shift as they develop. Food webs reflect the complexity of trophic interactions.

TROPHIC LEVELS The various steps of food chain where food or energy are transferred are called TROPHIC LEVEL. Energy is lost with each trophic ~90% is released to the environment as heat ~10% of the energy is used Only about 10% of the energy from one level is passed on to the next level

TROPHIC LEVELS In an ecosystem following trophic level are present-
Producers = 1st trophic level Primary consumers that eat producers(herbivores) = 2nd trophic level Secondary consumers that eat primary consumers (carnivores)= 3rd trophic level Tertiary consumers that eat secondary consumers(top carnivores /omnivores) = 4th trophic level Saprophytes that obtain their food from all the trophic level by decomposition = 5th trophic level.

ENERGY PATHS 3 ways to illustrate energy flow
1. Food Chain: Single path 3 ways to illustrate energy flow 3. Food Pyramid 2. Food Web: many paths

FOOD CHAINS A food chain shows the path of energy from one organism to the next energy flows from producers to consumers arrows point to who is eating (plant is eaten by herbivore) Usually decomposers are left out

Another way of showing the transfer of energy in an ecosystem is the ENERGY PYRAMID.

Energy Pyramids The graphical representation of number, biomass & stored energy of various trophic levels of food chain in an ecosystem is called ecological pyramids.

Energy pyramids show That the amount of available energy decreases down the food chain It takes a large number of producers to support a small number of primary consumers It takes a large number of primary consumers to support a small number of secondary consumers

Ecological Pyramids Pyramid of numbers Pyramid of biomass
Fig p. 79 Pyramid of biomass Pyramid of energy flow

Pyramid of numbers A pyramid of numbers indicates the number of individuals in each trophic level. # of carnivores # of herbivores # of producers

Pyramid of biomass A pyramid of biomass indicates how much biomass is present in each trophic level at any one time. biomass of carnivores biomass of herbivores biomass of producers

Pyramid of energy A pyramid of energy depicts the energy flow, or productivity, of each trophic level. producers herbivores carnivores

Ecological pyramids The standing crop, productivity, number of organisms, etc. of an ecosystem can be conveniently depicted using “pyramids”, where the size of each compartment represents the amount of the item in each trophic level of a food chain. Note that the complexities of the interactions in a food web are not shown in a pyramid; but, pyramids are often useful conceptual devices--they give one a sense of the overall form of the trophic structure of an ecosystem. producers herbivores carnivores

Pyramid of energy A pyramid of energy depicts the energy flow, or productivity, of each trophic level. Due to the Laws of Thermodynamics, each higher level must be smaller than lower levels, due to loss of some energy as heat (via respiration) within each level. Energy flow in : producers herbivores carnivores

FOOD CHAINS/WEBS & ENERGY PYRAMIDS
Food chains/webs can be written as a pyramid: Producers form the base of the pyramid Consumers form the upper layers

ENERGY PYRAMIDS The energy pyramid shows energy flow in an ecosystem:
Top Consumer Energy stored by Secondary Consumers Primary Consumers ENERGY STORED BY PRODUCERS A level of the energy pyramid is called a TROPHIC LEVEL Each trophic level represents the energy for those organisms

QUICK REVIEW Practice! If 100% of the energy is available at the first trophic level, what percentages of the energy are available at the second and third trophic levels? 1% 10% 100%

QUICK REVIEW! energy pyramid organism Producers 10%
All organisms in an ecosystem need _______ from food to live. An energy ________ shows how much food energy is passed from one ________ to another through food chains. __________ have the largest spot at the base of the pyramid. Altogether, only about _____ of the food energy at each level gets passed up to the next level. energy pyramid organism Producers 10%

Energy Flow and Energy Loss in Ecosystems: Food Chains
Consumers in a food chain can be classified as: 1. Detrivores – consumers that obtain energy and nutrients from dead organisms and waste matter Examples include earthworms, bacteria and fungi. Detrivores feed at every trophic level. Detrivores have their own, separate food chains and are very numerous.

2. Herbivores – primary consumers
Herbivores eat plants (producers) only. 3. Carnivores – secondary or tertiary consumers Secondary consumers eat non-producers, such as herbivores. Tertiary consumers eat secondary consumers. Also called top consumers or top carnivores. 4. Omnivores – consumers that eat both plants and animals Examples include humans and bears.

Energy Flow and Energy Loss in Ecosystems:Food Webs
Most organisms are part of many food chains. Food webs represent interconnected food chains. Food webs are models of the feeding relationships in an ecosystem. Arrows in a food web represent the flow of energy and nutrients. Following the arrows leads to the top carnivore(s).

This food web represents a terrestrial ecosystem that could be found in British Columbia.

Energy Flow and Energy Loss in Ecosystems: Food Pyramids
Food pyramids show the changes in available energy from one trophic level to another in a food chain. Energy enters at the first trophic level (producers), where there is a large amount of biomass and therefore much energy. It takes large quantities of organisms in one trophic level to meet the energy needs of the next trophic level.

Each level loses large amounts of the energy it gathers through basic processes of living.
80 – 90 percent of energy taken in by consumers is used in chemical reactions in the body and is lost as thermal energy. There is very little energy left over for growth or increase in biomass.

Ninety percent of this mouse’s food energy is used to maintain its life functions.

Lower trophic levels have much larger populations than upper levels.
This shows the importance of maintaining large, biodiverse populations at the lowest levels of the food pyramid.

Food pyramids are also known as ecological pyramids
Ecological pyramids may show biomass, population, or energy numbers. The amount of life an ecosystem can contain is based on the bottom level of the ecological pyramid, where producers capture energy from the Sun. Each level in the energy pyramid = a loss of 90 percent of total energy available.

Energy Flow & Nutrient Cycle

Food Chains Artificial devices to illustrate energy flow from one trophic level to another Trophic Levels: groups of organisms that obtain their energy in a similar manner Food Chains Although the term 'food chain' has entered into common usage, in most ecosystems food chains do not occur. The idea that energy flows along a chain of consecutive links made up of various consumers is unrealistic. As we will see shortly, trophic interactions are considerably more complex than a series of linear steps. Food chains are a useful beginning to illustrate the concept of trophic levels. Trophic levels are a way of identifying what kinds of food an organism uses. Primary producers obtain their energy from the sun or chemical sources and utilize inorganic compounds from the environment to make organic compounds. Herbivores feed on primary producers that utilize the sun for energy Carnivores feed on herbivores and other heterotrophic organisms.

Example Food Chain This simplified food chain illustrates links in a food chain. The chain begins with diatoms which are consumed by herbivorous copepods. The copepods are consumed by carnivorous zooplankton (in this case, chaetognaths) and the chaetognaths are consumed by planktivorous fishes. In a food chain, energy moves in a linear fashion from producers through consumers.

Food Chains Total number of levels in a food chain depends upon locality and number of species Highest trophic levels occupied by adult animals with no predators of their own Secondary Production: total amount of biomass produced in all higher trophic levels Food Chains In food chains, the total number of trophic levels depends upon the location and number of different species. In general, the highest trophic level is occupied by adult animals with no predators of their own. For example, killer whales would occupy the highest trophic level in an antarctic food chain. Secondary production refers to the total amount of animal biomass produced in all trophic levels above the primary producers. That is, it reflects all heterotrophic production.

Nutrients Inorganic nutrients incorporated into cells during photosynthesis - e.g. N, P, C, S Cyclic flow in food chains Decomposers release inorganic forms that become available to autotrophs again Nutrients Inorganic nutrients are incorporated into cells during photosynthesis and chemosynthesis. Examples of important nutrients are nitrogen, phosphorus, carbon and sulfur. The flow of nutrients in a food chain is cyclical. A pool of nutrients resides in a trophic level until animals die or excrete it. Then decomposers can release it in a form that is utilizable by autotrophic organisms.

Energy Non-cyclic, unidirectional flow
Losses at each transfer from one trophic level to another - Losses as heat from respiration - Inefficiencies in processing Total energy declines from one transfer to another - Limits number of trophic levels Energy Unlike nutrients, the flow of energy is not cyclical but rather is unidirectional. Energy is captured by primary producers and transferred to higher trophic levels. At each transfer, only a fraction of the energy is passed on and much is lost. These losses are in the form of heat and inefficiencies in processing and assimilating energy. Thus, the total available energy declines as one moves up trophic levels in a food chain. This places a limit on the number of trophic levels that can exist. At some point, there is too little energy available to sustain further transfers.

Energy Flow

Energy Flow through an Ecosystem
sun Food Chain Primary Producer Primary Consumer Secondary Consumer Tertiary Consumer zooplankton larval fish phytoplankton fish heat Example Food Chain This simplified food chain illustrates links in a food chain. The chain begins with diatoms which are consumed by herbivorous copepods. The copepods are consumed by carnivorous zooplankton (in this case, chaetognaths) and the chaetognaths are consumed by planktivorous fishes. In a food chain, energy moves in a linear fashion from producers through consumers. heat heat water Nutrients Fungi & bacteria Decomposer

Transfer Efficiencies
Efficiency of energy transfer called transfer efficiency Units are energy or biomass Pt = annual production at level t Pt-1 = annual production at t-1 Et = Pt Pt-1 Transfer Efficiencies Only a portion of the energy in one trophic level makes its way to the next. This is called the transfer efficiency. The currency may be energy or biomass.

Transfer Efficiency Example
Net primary production = 150 g C/m2/yr Herbivorous copepod production = 25 g C/m2/yr = Pcopepods Et = Pt Pt-1 = 25 = 0.17 Pphytoplankton 150 Transfer Efficiency Example Let's assume that we wish to calculate the transfer efficiency between primary producers and herbivorous copepods. Our currency will be grams of carbon. The annual production of primary producers is 150gC per square meter per year. The annual production of copepods is 25 gC per square meter per year. The transfer efficiency is then 25/150 or about 17%. Typical transfer efficiencies from primary producers to herbivores are about 20% while efficiencies between higher levels are about 10%. Typical transfer efficiency ranges *Level 1-2 ~20% *Levels 2-3, …: ~10%

Energy and Biomass Pyramids
Kaneohe Bay 10 J Tertiary consumers 100 J Secondary consumers 1000 J Primary consumers 10,000 J Limu Primary producers 1,000,000 J of sunlight

Energy Use By An Herbivore
Algae eaten by Uhu Cellular Respiration Feces Growth

Food Webs Food chains don’t exist in real ecosystems
Almost all organisms are eaten by more than one predator Food webs reflect these multiple and shifting interactions Food Webs Remember that food chains are an artificiality that don't really exist. In reality, the trophic linkages between organisms are much more complicated. Most organisms have more than one predator and the diets of animals shift as they develop. Food webs reflect the complexity of trophic interactions.

Antarctic Food Web

Some Feeding Types Many species don’t fit into convenient categories
Algal Grazers and Browsers Suspension Feeding Filter Feeding Deposit Feeding Benthic Animal Predators Plankton Pickers Corallivores Piscivores Omnivores Detritivores Scavengers Parasites Cannibals Ontogenetic dietary shifts Food Webs ... There are many trophic categories that are too complicated to fit into the simple concept of a food chain. Many animals are omnivorous. That means that they consume a wide variety of prey. An omnivore might consume diatoms and crustacean larvae. Thus, it's feeding at trophic levels one and two. Detritivores feed on dead organic matter that can be derived from a wide range of sources at varying trophic levels. During development (ontogeny) animals often shift their diet as they grow larger. Consider a tuna which may begin by feeding on copepods and zooplankton but which progresses to large fish at adulthood. Parasites complicate the picture because they may have a number of different hosts of different trophic status.

Food Webs… Competitive relationships in food webs can reduce productivity at top levels Phytoplankton (100 units) Phytoplankton (100 units) Herbivorous Zooplankton (20 units) Herbivorous Zooplankton (20 units) Food Webs ... The presence of two competitors feeding on the same prey items may alter the availability of energy to higher trophic levels. Consider the example on the left where carnivorous zooplankton of species A feed on herbivorous zooplankton and are themselves consumed by fishes. Let's introduce a second species of carnivorous zooplankton. Species B isn't consumed by fish but shares the supply of herbivorous zooplankton with species A. The result is that the availability of energy to fishes is diminished. Food webs contain many of these sorts of competitive relationships and prey preference. Carnivorous Zooplankton A (2 units) Carnivorous Zooplankton A (1 units) Carnivorous Zooplankton B (1 units) Fish (0.2 units) Fish (0.1 units)

Recycling: The Microbial Loop
All organisms leak and excrete dissolved organic carbon (DOC) Bacteria can utilize DOC Bacteria abundant in the euphotic zone (~5 million/ml) Numbers controlled by grazing due to nanoplankton Increases food web efficiency The Microbial Loop All organisms leak organic carbon compounds into the water. This organic carbon (DOC) is an important food source that would be a net loss to each trophic level. Bacteria are abundant in seawater and many bacteria are capable of utilizing this DOC. Bacterial numbers are controlled via grazing by nanoplankton (ciliates and flagellates). These small zooplanktors are then consumed by larger zooplankton. In this way, the lost DOC is recycled and returns to the food web.

Microbial Loop Phytoplankton Herbivores Planktivores Piscivores
Solar Energy Phytoplankton Herbivores CO2 nutrients Planktivores DOC Piscivores Bacteria Nanoplankton (protozoans)

An Ecological Mystery An Ecological Mystery
Let's take a look at a food web in the north Pacific ocean that has changed substantially in the past decade.

Keystone Species Kelp Forests

An Ecological Mystery Long-term study of sea otter populations along the Aleutians and Western Alaska 1970s: sea otter populations healthy and expanding 1990s: some populations of sea otters were declining Possibly due to migration rather than mortality 1993: 800km area in Aleutians surveyed - Sea otter population reduced by 50% An Ecological Mystery Sea otters are marine mammals that live in kelp beds along the western coast of North America from Baja Mexico to Alaska. Once hunted to near extinction, their protection has been one of the success stories of conservation. In the 1970's, sea otter populations were healthy and expanding throughout their range. Scientists noted that by the 1990's some populations of sea otters were declining. One possibility was that the animals had moved rather than died. In 1993, an 800 km long section of the Aleutian Islands was surveyed and the results were alarming. The sea otter population had declined by 50%.

Vanishing Sea Otters 1997: surveys repeated
Sea otter populations had declines by 90% : ~53,000 sea otters in survey area : ~6,000 sea otters Why? - Reproductive failure? - Starvation, pollution disease? Vanishing Sea Otters In 1997 the Aleutian survey was repeated and the results were worse. Sea otter populations had declined by 90%. In 1970, some 53, 000 sea otters lived in the study area. By 1997, that population was down to about 6,000 animals. A number of possible causes were considered. These included reproductive failure, starvation, pollution and disease. The problem with these hypotheses was that there was no evidence of dead otters that might support the idea of some epidemic or source of mortality that would kill many over a wide range.

Cause of the Decline 1991: one researcher observed an orca eating a sea otter Sea lions and seals are normal prey for orcas Clam Lagoon inaccessible to orcas- no decline Decline in usual prey led to a switch to sea otters As few as 4 orcas feeding on otters could account on the impact - Single orca could consume 1,825 otters/year Cause of the Decline In 1991, one scientist noticed an orca (killer whale) eating a sea otter. This was unusual because sea lions and seals are the normal prey for orcas and a small animal such as a sea otter wouldn't provide much nutrition. At one site called Clam Lagoon, populations of otters remained healthy. Interestingly, that site was inaccessible to orcas. It turned out that orcas had indeed been responsible for the decline in otters. A decline in the abundance of their usual prey forced them to switch to otters. Not all the orcas needed to switch to generate the mortality observed along the Aleutians. As few as 4 orcas feeding solely on otters could have produced an impact of the magnitude observed. A single orca could consume about 1,825 otters per year.

Energy Flow Through an Ecosystem
Food Chains, Food Webs, Energy Pyramids

6CO2 + 6H2O + sunlight & chlorophyll C6H12O6 + 6O2
Begins with the SUN Photosynthesis 6CO2 + 6H2O + sunlight & chlorophyll C6H12O6 + 6O2

The chemical reaction by which green plants use water and carbon dioxide and light from the sun to make glucose. ENERGY is stored in glucose; glucose is stored as starch.

Organisms that can make glucose during photosynthesis are called PRODUCERS.

Producers use most of the energy they make for themselves.

Producers use cellular respiration to supply the energy they need to live.

6O2 + C6H12O6 --> 6H2O + 6CO2 + energy
CELLULAR RESPIRATION is the chemical reaction that releases the energy in glucose.

The energy that is not used by producers can be passed on to organisms that cannot make their own energy.

Organisms that cannot make their own energy are called CONSUMERS.

Consumers that eat producers to get energy:
Are first order or primary consumers Are herbivores (plant-eaters)

Most of the energy the primary consumer gets from the producer is used by the consumer.

Some of the energy moves into the atmosphere as heat.

Some energy in the primary consumer is not lost to the atmosphere or used by the consumer itself. This energy is available for another consumer.

A consumer that eats another consumer for energy:
Is called a secondary or second order consumer May be a carnivore or a herbivore May be a predator May be a scavenger

Most of the energy the secondary consumer gets from the primary consumer is used by the secondary consumer.

Some of the energy is lost as heat, but some energy is stored and can passed on to another consumer.

A consumer that eats a consumer that already ate a consumer:
Is called a third order or tertiary consumer May be a carnivore or a herbivore May be a predator May be a scavenger

Consumers that eat producers & other consumers
Are called omnivores Omnivores eat plants and animals

Consumers that hunt & kill other consumers are called predators
Consumers that hunt & kill other consumers are called predators. They animals that are hunted & killed are called prey.

Consumers that eat other consumers that have already died are called scavengers.

Another way of showing the transfer of energy in an ecosystem is the ENERGY PYRAMID.

Energy pyramids show That the amount of available energy decreases down the food chain It takes a large number of producers to support a small number of primary consumers It takes a large number of primary consumers to support a small number of secondary consumers

SAM GIRLS COLLEGE, BHOPAL

Similar presentations

Presentation on theme: "SAM GIRLS COLLEGE, BHOPAL"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

SAM GIRLS COLLEGE, BHOPAL

Similar presentations

Presentation on theme: "SAM GIRLS COLLEGE, BHOPAL"— Presentation transcript:

Similar presentations

About project

Feedback