5Cod Math The volume of the earth's oceans is 1.35 X 109 cubic Km. A typical 50 cm female cod lays 200,000 eggs/yrA typical mature cod might weigh...10 kgAssuming that the fish stack perfectly with no void spaces and that the density of the cod is equal to the density of seawater, then a cubic Km of cod would weigh...(1 cubic km) X (1,000,000,000 cubic m/cubic km) X (1000 kg/cubic m) X to correct for seawater density) = 1.32 X 1012 kg.If a cod weighs 10 kg, then we can calculate the cod fish per cubic km as (1.32 X 1012 kg) X (1 cod/10 kg) = 1.32 X 1011 cod per cubic km of ocean.Then the number of cod that it would take to fill the ocean is equal to (1.32 X 1011 cod/cubic km of ocean) X (1.35 X 109 cubic km of ocean) = 1.78 X 1020 codfish.
6If we assume that the codfish take 5 years to reach their maximum size of 10 kg, that they start spawning at 5 years of age, that each female would lays 200,000 eggs per year once it is 5 years old, and that they live to be at least 25 years old…Year 1: 2 codfish spawnYear 2: ,000 codfishYear 3: (200,000)Year 4: 2 + 3(200,000)Year 5: 2 + 4(200,000)Year 6: 2+ 5 (200,000) + (100,000 X 200,000)Year 7: 2 + 6(200,000) + 2(100,000 X 200,000)Year 8: 2+ 7(200,000) + 3(100,000 X 200,000)Year 9: 2 + 8(200,000) + 4(100,000 X 200,000)Year 10: 2 + 9(200,000) + 5(100,000 X 200,000) +(100,000 X 100,000 X 200,000)2 + 1,800, ,000,000, ,000,000,000,000,000 = 2,000,100,001,800,000 or 2 X 1015Year 11: 2(100,000 X 100,000 X 200,000)Year 12: 3(100,000 X 100,000 X 200,000)Year 13: 4(100,000 X 100,000 X 200,000)Year 14: 5(100,000 X 100,000 X 200,000) = 1 X 1016Year 15: 6(100,000 X X 100,000 X 200,000) + (100,000 X 100,000 X 100,000 X 200,000) = 2 X 1020
11Over the entire lifetime of this mola pair, how many of their babies must survive in order to keep the population stable ?2
1220 yearlifespan23,000,000 eggsyear/mola= 460,000,000 eggsXNeed to replace the male and female breeding molas, therefore we need 2 fish out of the 460 million eggs.Mola egg survival to maintain population= 1 per 230,000,000
1410,000 eggsyear/salmon1 yearspawning= 10,000 eggsXNeed to replace the male and female breeding salmon, therefore we need 2 fish out of the 10,000 eggs.Salmon egg survival to maintain population= 1 per 5,000
161 baby2 years/shark20 yearlifespan= 10 baby sharksXNeed to replace the male and female breeding sharks, therefore we need 2 fish out of the 10 babies to survive.Shark baby survival to maintain population= 1 per 5
17Two strategiesMake bazillions of “low cost” disposable eggs and abandon them. Hardly any survive, but when you start with millions…Make very few eggs with tons of energy and guard them. There aren’t many eggs, but when most are going to survive…RK
18R-selection In unstable or unpredictable environments the ability to reproduce quickly is crucial, and there is little advantage in adaptations that permit successful competition with other organisms, because the environment is likely to change again. R= high fecundity, small body size, short generation time, and the ability to disperse offspring widely. R- Dandelions, mice, grass carpK-selection In stable or predictable environments the ability to compete successfully for limited resources is crucial, and populations of K-selected organisms typically are very constant and close to the maximum that the environment can bear. K= large body size, long life expectancy, and the production of fewer offspring that require extensive parental care until they mature. K-elephants, whales, Arctic Terns, tiger sharks
19R (many eggs): Unstable environments R (many eggs): Unstable environments. Many years things go wrong and the population drops, but in good years fry survival is high and the fish population can explode.K (few eggs): Stable environments. Many animals competing with each other for resources. Difficult to find an opportunity for a big population increase, and they would probably starve anyway.
20R or K ? River Unpredictable flow Unpredictable plankton blooms Unpredictable water tempsUnpredictable oxygen levels!R or K ?
21Coral Reef Stable temperatures Stable water quality Consistent plankton populations R or K ?
22R or K ? Shallow temperate seas Unpredictable plankton blooms Unpredictable water temps
23R or K ? Deep Sea Constant water temp Constant water quality Stable food supply
24? Intermediate Strategies K R Stable tropical seas Large well-developed young Live bearers?RUnpredictable conditions for fryEgg broadcasters- huge numbers
29Males carry eggs in clusters or balls attached to a hook on the head Males carry eggs in clusters or balls attached to a hook on the head. This may be an adaptation to environments with low oxygen and high turbidity
93Two basic strategies R K Make bazillions of “low cost” disposable eggs and abandon them. Hardly any survive, but when you start with millions…Make very few eggs/babies with tons of energy and guard them. There aren’t many eggs, but when most are going to survive…There are plenty of intermediate strategiesRK