4.1 Species, communities, and ecosystems

Question 1

Table on big picture?

Question 2

What is a species?

Answer 2

A group of organisms that can potentially interbreed and produce fertile offspring

Question 3

What are fertile offspring?

Answer 3

Those which can in turn interbreed and pass on their genes to another generation.

Question 4

Explain how members of species may be reproductively isolated

Answer 4

-Members of a species may be reproductively isolated in separate populations due to geographical barriers, behavioral differences, or niche partitioning.

-For instance, populations of black rats (Rattus rattus) found in different parts of the world are reproductively isolated, as their members cannot come together in the same area to mate.

-However, we expect them to be able to mate and produce fertile offspring if their populations are united.

-If they are not able to mate and produce fertile offspring, it may be that speciation has occurred.

-In this case, they may have evolved to the point where they are too genetically different to produce fertile offspring.

Question 5

Organisms of the same species will be classified into the same ___

Answer 5

Taxa

Question 6

Species in these pictures

Answer 6

-The two dogs on the left look very different from each other, so you may not expect them to be in the same species, however, they are both members of the genus and species, Canis familiaris, so for both the Great Dane and the Afghan Hound, the scientific names are the same, however their physical traits are somewhat different.

-The wolf on the right is in the same genus as the two domestic dogs on the left, however, it belongs to a different species, Canis lupus .

Question 7

Describe the relationship between closely-related species

Answer 7

-Normally, these two species do not live in the same ecosystem; they remain reproductively isolated.

-But in zoos, these large cats sometimes are kept together in enclosures.

-Occasionally in nature and more often in captivity, closely associated species can and will interbreed, but their offspring are normally infertile.

Question 8

What is a gene pool and what group shares the same gene pool?

Answer 8

-A collection of genes (along with their associated allelic forms) found in a population.

-Therefore, all members of a species share a common gene pool and number of chromosomes in their haploid cells.

Question 9

Describe the chromosomes of a liger (the offspring of a male lion and female tiger)

Answer 9

-A male lion ( Panthera leo ) and a female tiger ( Panthera tigris ), both of which have 38 chromosomes (2n), have produced an offspring called a liger.

-You can see that this creature shares some characteristics with both a lion and a tiger.

Question 10

Describe the chromosomes of a mule

Answer 10

Another example is the mule, resulting from the interbreeding of a male donkey ( Equus africanus asinus) with 62 chromosomes (2n) and a female horse ( Equus ferus caballus) with 64 chromosomes (2n).

Question 11

Why are hybrid species, like the mule, often infertile?

Answer 11

-Horses and donkeys have a different number of chromosomes in their cells, which scientists can see from their karyograms.

-This difference in chromosome numbers is why hybrid species, such as the mule, are often infertile.

Question 12

Why do we find mostly distinct species as opposed to hybrid species in nature?

Answer 12

Whether hybrid animals come from parents with the same number of chromosomes in their gametes or not, they are typically incapable of producing fertile offspring themselves.

Question 13

What is a population?

Answer 13

A group of organisms of the same species that live in a particular area at the same time.

Question 14

Groups of populations can live together to form ___

Answer 14

Communities

Question 15

What is a community?

Answer 15

A group of populations living and interacting in a particular area.

Question 16

What is an ecosystem?

Answer 16

A community and its abiotic environment.

Question 17

What are abiotic factors?

Answer 17

Non-living factors, such as pH, salinity, wind speed, type of soil, etc.

Question 18

What are biotic factors?

Answer 18

Living factors in an ecosystem, such as the plants and animals.

Question 19

Diagram showing an individual, population, and community

Answer 19

Question 20

In a pond, two species of frogs feed on insects.

The insects feed on the algae that live in the water.

What constitutes a population in this ecosystem?

Answer 20

All the frogs of one species

Question 21

What are organic molecules, such as glucose and amino acids, needed for?

Answer 21

Growth, reproduction and movement.

Question 22

How many modes of nutrition are there by which organic compounds can be obtained?

Answer 22

-2:

-Autotrophic

-Heterotrophic

Question 23

What are autotrophic organisms?

Answer 23

-Organisms that are capable of making their own complex organic molecules from carbon dioxide and other simple compounds.

-Almost all plants and some other organisms, for example, Cyanobacteria , Dinoflagellata and Euglenida, are capable of autotrophic nutrition.

Question 24

What are heterotrophic organisms?

Answer 24

Organisms that obtain their organic compounds through feeding on other organisms.

Question 24

What are heterotrophic organisms?

Answer 24

Organisms that obtain their organic compounds through feeding on other organisms.

Question 25

What are the 5 kingdoms?

Answer 25

-Bacteria (Archaebacteria and Eubacteria) -Protoctista -Fungi -Plantae -Animalia

Question 26

What is the mode of obtaining organic molecules for bacteria?

Answer 26

Some autotrophic and some heterotrophic

Question 27

What is the mode of obtaining organic molecules for Protoctista?

Answer 27

Some autotrophic and some heterotrophic

Question 28

What is the mode of obtaining organic molecules for fungi?

Answer 28

Heterotrophic

Question 29

What is the mode of obtaining organic molecules for plantae?

Answer 29

Mostly autotrophic

Question 30

What is the mode of obtaining organic molecules for animalia?

Answer 30

Heterotrophic

Question 31

What are mixotrophs?

Answer 31

-There are some species that can feed both autotrophically and heterotrophically. -These organisms are known as mixotrophs. Euglena gracilis is such an organism. -It lives in ponds.

Question 32

Picture of Euglena gracilis: an organism that is both heterotrophic and autotrophic

Answer 32

Question 33

Name the mode of nutrition practiced by secondary consumers.

Answer 33

Heterotrophic

Question 34

What mode of nutrition do producers and consumers use and why?

Answer 34

-When considering a food chain or food web, the producers are always autotrophs and all consumers are heterotrophs. -This is because producers can make their own organic compounds, while consumers must feed on other living organisms by ingestion to obtain their organic compounds.

Question 35

How can heterotrophs be grouped?

Answer 35

-According to the way they get their organic molecules from other organisms. -The most obvious way is by ingesting or eating other organisms. -But that would pose a problem for those organisms that do not have a mouth, or other anatomical feature, that would allow eating.

Question 36

Biologists categorize heterotrophs in ___ broad groups.

Answer 36

Three

Question 37

What are the three broad groups that biologists categorize heterotrophs into?

Answer 37

-Consumers -Detritivores -Saprotrophs

Question 38

Describe how the range of consumers is enormous

Answer 38

-Some organisms, such as elephants, fish, or otters, get carbon compounds by ingestion or eating. -They consume other living organisms or recently living organisms. -In the case of an elephant, that could be grass or branches of trees, whereas an otter mainly consumes fish. -Once ingested, their food is digested. -Some consumers are much smaller: Paramecium and other unicellular organisms take in their food, usually bacteria or algae, by endocytosis. -Once inside, their food is digested in food vacuoles using the digestive enzymes from lysosomes.

Question 39

Parasites as consumers

Answer 39

-Some parasites are considered consumers, for example, the tapeworm, but they do not have a digestive tract. -Instead of ingesting or eating, they rely on their host to break down food then they absorb the nutrients directly through their skin or cuticle.

Question 40

Define ingestion

Answer 40

-The taking in of a substance (be it solid or liquid food, medication, toxic substances, or indigestible materials). -In animals, ingestion takes place through the mouth, but it could occur by any other means to allow entry into the body.

Question 41

What are consumers?

Answer 41

Organisms that gain nutrients by feeding on other organisms using ingestion or absorption.

Question 42

What is the difference between ingestion, digestion, and egestion?

Answer 42

Ingestion is a term used for feeding, digestion is the breakdown of food once it has been ingested, and egestion is the waste or undigested material that leaves the body.

Question 43

How are consumers further defined by what they eat?

Answer 43

-Primary consumers (1º) feed only on autotrophs, these organisms are also known as herbivores. -Secondary consumers (2º) feed on primary consumers, and tertiary consumers (3º) feed on secondary consumers. -Organisms that feed solely on other consumers are known as carnivores and can be classified even further by the type of consumer they eat, for example, the giant anteater (Myrmecophaga tridactyla) is considered a carnivore, but more specifically an insectivore, which makes them secondary consumers in the food chain.

Question 44

What are herbivores?

Answer 44

Consumers that feed solely on producers.

Question 45

What are primary consumers?

Answer 45

These feed on producers.

Question 46

What are secondary consumers?

Answer 46

These feed on primary consumers.

Question 47

What are tertiary consumers?

Answer 47

These feed on secondary consumers.

Question 48

What are carnivores?

Answer 48

Consumers who feed solely on other consumers.

Question 49

Do tertiary consumers feed exclusively on secondary consumers?

Answer 49

-Tertiary consumers do not always feed exclusively on secondary consumers, just think of a grizzly bear. -The grizzly will eat elk (a species of deer), which are primary consumers. -Sometimes the grizzly will eat berries and other plants to complement its diet.

Question 50

What are omnivores?

Answer 50

Consumers that feed on both producers and consumers.

Question 51

When can organisms be placed in more than one trophic level?

Answer 51

Organisms with a varied diet.

Question 52

What are detritivores?

Answer 52

-Heterotrophs that obtain their organic nutrients from detritus, which is waste or other organic debris, by internal digestion. -They gain nutrients by feeding on dead organic material and breaking it into smaller organic molecules.

Question 53

Examples of detritivores

Answer 53

Earthworms and dung beetles.

Question 54

Where does the organic matter that detritivores feed on come from?

Answer 54

-As organisms live their lives, they leave behind large quantities of organic material called detritus. -Humans lose hair and skin cells and produce feces, trees shed their leaves and birds lose feathers. -Additionally, remains of dead decaying bodies or plants also contribute to detritus.

Question 55

Why are detritivores important?

Answer 55

For recycling nutrients and returning them to the soil for autotrophs to use.

Question 56

What is internal digestion?

Answer 56

The process by which an organism digests its food inside of its body, usually with the aid of a digestive tract.

Question 57

What type of material do detritivores feed on? (reword)

Answer 57

Most detritus or discarded material contains organic compounds that can be used as a source of energy or raw materials by detritivores following internal digestion.

Question 58

What are saprotrophs?

Answer 58

-Heterotrophs that obtain their organic nutrients from dead organisms by external digestion (extracellular digestion). -They get their nutrients by secreting digestive enzymes into their environment to break down organic debris around them.

Question 59

What is external digestion?

Answer 59

External digestion or extracellular digestion is the process by which organisms secrete enzymes into their environment to break down organic debris around them.

Question 60

What are saprotrophs sometimes referred to as?

Answer 60

These organisms are sometimes referred to as decomposers as they feed on dead organic matter (derived from dead organisms).

Question 61

Examples of saprotrophs

Answer 61

Fungi and bacteria.

Question 62

Explain how saprotrophs feed

Answer 62

-They secrete digestive enzymes on decaying organic matter on which they are feeding, to cause the breakdown of complex organic compounds into simpler organic molecules and minerals, which increases soil fertility. -The soluble digested materials released are then absorbed and used by the saprotrophs themselves and can also re-enter the food chain when plants absorb them and use them for photosynthesis.

Question 63

Why are saprotrophs important for the environment?

Answer 63

Nutrient cycling by detritivores and saprotrophs is an important process in sustaining ecological stability.

Question 64

What is the difference between detritivores and saprotrophs?

Answer 64

-Detritivores ingest and internally digest organic debris, while saprotrophs perform external digestion to obtain nutrients. -Both are important contributors to nutrient cycling in ecosystems.

Question 65

Certain fungi grow on fallen tree leaves. Which of the terms describes their mode of nutrition? I. Saprotroph II. Autotroph III. Heterotroph

Answer 65

I and III only

Question 66

Certain fungi grow on fallen tree leaves. Which of the terms describes their mode of nutrition? I. Saprotroph II. Autotroph III. Heterotroph

Answer 66

I and III only

Question 67

Organisms that obtain their organic nutrients from dead organisms by external digestion are known as ___.

Answer 67

Saprotrophs/decomposers

Question 68

Identify the following organism as an autotroph or heterotroph. If the organism is a heterotroph, identify it as a consumer, detritivore, or saprotroph.

Answer 68

Autotroph

Question 69

Identify the following organism as an autotroph or heterotroph. If the organism is a heterotroph, identify it as a consumer, detritivore, or saprotroph.

Answer 69

Consumer

Question 70

Refer to the illustration below. If the toad eats a spider it is considered a ___ consumer.

Answer 70

Tertiary

Question 71

What is ecology?

Answer 71

The branch of biology where scientists study ecosystems and the interactions of the biotic and abiotic factors.

Question 72

Describe a symbiotic relationship (mutualism) between spider crabs and algae

Answer 72

-The algae live on the crabs' backs. -In this way, predators cannot see the crabs because they blend in with their environment through camouflage. -The benefit for the algae is that they get a place to live, so both organisms help each other, which is an example of the type of symbiotic relationship called mutualism, where both organisms benefit from the relationship.

Question 73

What are decorator crabs and how does this property benefit them?

Answer 73

-Decorator crabs 'decorate' their shells with sponges, corals, and even urchins in order to camouflage themselves from predators. -This benefits the other organism by giving them a mobile place to attach and live.

Question 74

Explain how there are some organisms that live in symbiotic relationships with other organisms and may seem to be autotrophic when in actuality they are not

Answer 74

-For example, lichen, which is in a mutualistic relationship between algae or cyanobacteria (autotrophic) and a fungus (heterotrophic). -The fungus provides water, nutrients, and shelter for the autotroph and the autotroph provides food for the fungus.

Question 75

Picture of lichen growing on a tree branch

Answer 75

Question 76

Explain commensalism and parasitism

Answer 76

Other forms of symbiotic relationships include commensalism, where one organism benefits and the other is unaffected and parasitism, when one organism benefits and the other is harmed.

Question 77

Drawing of commensalism (a bird's nest in a tree)

Answer 77

Question 78

Picture of a mosquito An example of parasitism is the relationship between a mosquito and a human. The mosquito depends on human blood for its nutrition while causing humans itchy bites and in some regions acting as a vector in spreading diseases such as malaria and zika.

Answer 78

Question 79

Define symbiosis

Answer 79

This means 'living together' and refers to the following outcomes of interactions between populations.

Question 80

Define mutualism

Answer 80

A type of symbiotic relationship where both organisms benefit.

Question 81

Define commensalism

Answer 81

A type of symbiotic relationship where one organism benefits and the other is unaffected.

Question 82

Define parasitism

Answer 82

A type of symbiotic relationship where one organism benefits and the other is harmed.

Question 83

Example of a predator-prey interaction

Answer 83

-The relationship between wolves and elk in Yellowstone National Park and how it affects the growth of willow trees. -In 1995, wolves were reintroduced to Yellowstone National Park. -Right from the start of the project, the wolf population in the park has grown, and the elk population, their favored prey, has declined. -This decline in elk numbers has resulted in changes in flora, most specifically, willow, cottonwood, and aspen trees along the fringes of heavily timbered areas and along the river banks. -A direct link can only be made between the introduction of the wolf and decline of the elk population, but research also suggests that the wolf predation has significantly altered elk feeding behaviour as well.

Question 84

Examples of communities

Answer 84

-Some communities are very complex, such as those found in the Amazonian jungle or on coral reefs. -Communities can also be small and less complex. -An example would be the communities of bacteria living together in some hot springs.

Question 85

Define a predator-prey relationship

Answer 85

One in which one organism hunts and feeds on another.

Question 86

What is the sequence of the levels of ecological organisation from least to most inclusive?

Answer 86

Species, population, community, ecosystem

Question 87

In a forest, owls and foxes both feed on mice. The mice feed on berries and nuts. What constitutes a population in this ecosystem?

Answer 87

All the mice of one species

Question 88

In the following picture, a cleaner wrasse is picking parasites off of a blue spotted stingray. This is an example of ___ relationship.

Answer 88

Symbiotic

Question 89

What abiotic factors are there in an ecosystem?

Answer 89

Aspects, such as rainfall, pH of the soil or water in which they live, temperature range, humidity, etc., all have an effect on living organisms.

Question 90

Give examples of how some abiotic environments can make life almost impossible

Answer 90

-In some regions of Earth, the abiotic environment makes life almost impossible. -Just think of Antarctica, where temperatures drop as low as –80   ºC and there is no light for up to six months of the year. -Such abiotic conditions make it a harsh environment in which it is difficult for life to exist. -Often organisms have to have special adaptations to be able to survive in these severe surroundings.

Question 91

Why do organisms thrive in ecosystems like coral reefs?

Answer 91

Because there are ample food resources and sufficient inorganic nutrients.

Question 92

What elements do organisms need?

Answer 92

-Organisms not only need carbon sources, but they require phosphorus and nitrogen for nucleic acids. -They also need sulfur for proteins and some 15 other elements. -For example, selenium is needed for the functioning of some enzymes, and magnesium is needed for bone formation. -It is important for these elements to be exchanged between the community and the abiotic environment.

Question 93

A community interacts with its abiotic environment to form an ___.

Answer 93

Ecosystem

Question 94

Why is nutrient cycling important?

Answer 94

-Organisms are dependent upon their environment to supply all the necessary chemicals for survival. -Scientists call the constant reuse of these chemicals nutrient cycles. -These cycles are often very complex, but the important message is that nutrients can be recycled almost indefinitely, unlike energy, which cannot be recycled and must be constantly supplied by the sun.

Question 95

Diagram of an example of a simplified version of a nutrient cycle

Answer 95

Question 96

Explain how nutrient cycling works

Answer 96

-Autotrophs make their organic compounds from simple inorganic nutrients that they absorb from their environment. -For example, plants absorb carbon dioxide and water from the abiotic environment to produce carbohydrates by photosynthesis. -Through the food chain, the nutrients are transferred from one organism to the next until they are released back into the abiotic environment following decomposition and other processes. -Therefore, the supply of inorganic nutrients is maintained by nutrient cycling and is vital in maintaining healthy ecosystems.

Question 97

Autotrophs obtain inorganic nutrients from the ___.

Answer 97

Abiotic environment

Question 98

Explain how ecosystems can have different sources of energy

Answer 98

-Energy cannot be recycled. -For most ecosystems, the sun is the main source of energy. -However, for a few ecosystems, such as the black smokers on the bottom of the ocean, the sun is a limited source of energy and most of the ecosystem’s energy is in the form of chemical energy. -Autotrophs that use chemical energy to make organic compounds used by consumers are called chemoautotrophs. -This is different than photoautotrophs which use energy from the sun for photosynthesis.

Question 99

Picture of a bed of tube worms near the base of a black smoker

Answer 99

Question 100

What do ecosystems need to sustain themselves for a very long time?

Answer 100

-An energy source and sufficient nutrient recycling -Some stable ecosystems have been known to exist for millions of years without major changes.

Question 101

Define nutrient cycling

Answer 101

This is a process that helps to move organic molecules and minerals through the food chain and back into the soil where they can be taken up by plants to re-enter the food chain.

Question 102

What is a mesocosm?

Answer 102

-An experimental tool used to model ecosystems in order to monitor and evaluate variables. -It can act as a model of a larger ecosystem, in which energy enters and leaves but matter does not.

Question 103

What are mesocosms used to evaluate?

Answer 103

How organisms or communities might react to environmental change, through deliberate manipulation of environmental variables, such as increased temperature, carbon dioxide or pH levels.

Question 104

What are the advantages of using a mesocosm as an experimental tool?

Answer 104

-Treatments are easily replicated. -The effect of several environmental factors can be tested. -Food webs can be established. -Direct and indirect effects can be studied. -Contamination influence can be evaluated. -Constants can be controlled to see the effect of one environmental factor at a time. -The sustainability of an ecosystem can be tested.

Question 105

What are the two main types of mesocosms?

Answer 105

Aquatic and terrestrial

Question 105

What are the two main types of mesocosms?

Question 106

Explain how mesocosms can be set up

Answer 106

-Mesocosms can be set up in open tanks, but sealed glass vessels are preferable because entry and exit of matter can be prevented, while still allowing light to enter and heat to leave. -You are expected to set up a sealed mesocosm to try to establish a sustainable system. -But, remember that irrespective of the type of mesocosm you set up, you should ensure that you respect the IB animal experimentation policy. -This implies that, if you are to include a living animal in your mesocosm, you have to ascertain that you will not be inflicting pain or undue stress on the organism. -Also, try to use upcycled materials whenever possible.

Question 107

Picture of a mesocosm (sealed)

Answer 107

Question 108

How can you ensure the sustainability of your sealed and aquatic mesocosms?

Answer 108

-Ensure that you have sufficient plant material to produce adequate oxygen to support all life forms in the system. -You may consider using an oxygen sensor and a carbon dioxide sensor to monitor the fluctuations in these two gases. -Aquatic mesocosms should have some water circulation to ensure the water does not become stagnant.

Question 109

A mesocosm can act as a model of a larger ecosystem in which ___ enters and leaves but ___ does not

Answer 109

Energy Matter

Question 110

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