4.3 Species interactions-3

Category: Entertainment

Presentation Description

No description available.


Presentation Transcript


1 Amensalism


Amensalism When one species suffers and the other interacting species experiences no effect. Described strongly asymmetrical competitive interactions, Examples: Spanish ibex and weevils of the genus  Timarcha   feed upon the same type of shrub. Whilst the presence of the weevil has almost no influence on food availability, the presence of ibex has an enormous detrimental effect on weevil numbers, as they consume significant quantities of plant matter and incidentally ingest the weevils upon it. Penicilium inhibits growth of various bacteria by secreting penicillin Streptomycin is secreted by Streptomyces gresius which checks growth of various other bacteria. The bread mold penicillium 2


Amensalism 3 Animal amensalism also occurs when a large animal by mistake steps on a smaller animal /plant killing it without getting any benefit from the act. Redwood trees falling into the ocean become floating battering-rams during storms, killing large numbers of mussels and other inter-tidal organisms. Sheep or cattle trampling on grass


Allelopathy involves the production and release of chemical substances by one species that inhibit the growth of another. These secondary substances are chemicals produced by plants that seen to have no direct use in metabolism. This same interaction can be seen as both amensalism, and extremely one-sided interference competition-in fact it is both. Self-ammensalism is seen in wild variety of Grevillea robusta that inhibits growth of its own seedlings through an allochemic secreted by its roots. Allelopathy 4

Example: Allelopathy in the California Chaparral:

Example: Allelopathy in the California Chaparral Black Walnut ( Juglans nigra ) trees excrete an antibiotic called juglone . Juglone is known to inhibit the growth of trees, shrubs, grasses, and herbs found growing near black walnut trees. Certain species of shrubs, notably Salvia leucophylla (mint) and Artemisia californica (sagebrush) - allelopathic substances that accumulate in the soil during the dry season. These substances inhibit the germination and growth of grasses and herbs in an area up to 1 to 2 meters from the secreting plants. Barley, sorghum, sunflower etc. don’t allow weeds to grow near them by secreting allochemics from roots. Hence, called smoother crops. Black walnut tree 5


6 Neutralism


Neutralism Is the most common type of interspecific interaction. Two animals do interact or share the same habitat but do not affect each other. Any interactions that do occur are indirect or incidental. Example: Tarantulas living in a desert and the cacti living in a desert White-tailed deer do not affect snakes, nor do the snakes affect the deer. 7


8 Commensalism


Commensalism It is an interspecific interaction where one species benefits and the other is unaffected. Derived from the Medieval Latin commensalis, meaning "sharing a table", from the prefix com -, meaning "together", and mensa , meaning "table" or "meal“ Commensalisms are ubiquitous in nature: birds nesting in trees are commensal. Commensal organisms frequently live in the nests, or on the bodies, of the other species. Examples of Commensalism: Ant colonies harbor rove beetles as commensals. These beetles mimic the ants behavior, and pass as ants. They eat detritus and dead ants. 9


EXAMPLES OF COMMENSALISM Cattle egrets foraging in fields among cattle or other livestock The egret benefits from catching insects that cattle “scare-up” while grazing. Cattle unaffected. 10


Bromeliads are a group of flowering plants that attach to trees (epiphytes). They gain access to sunlight and catch water. The trees are not harmed or benefited. 11 EXAMPLES OF COMMENSALISM


E. coli ( Escherichia coli ) is a common bacteria found living in the guts of mammals, including humans, where it gets all it needs to thrive. In most circumstances, humans are not harmed by its presence and no benefit has been discovered. 12 EXAMPLES OF COMMENSALISM


EXAMPLES OF COMMENSALISM Kol-bal jackals and tigers 13 jackals:


Inquilinism It involves one species using the body or a body cavity of another organism as a platform or a living space while the host organism neither benefits nor is harmed . TYPES OF COMMENSALISM 14 Barnacles and whales


TYPES OF COMMENSALISM Metabiosis Occurs when one species unintentionally creates a home for another species through one of its normal life activities. Indirect dependency, in which one organism creates or prepares a suitable environment for a second. Examples: maggots, which feast and develop on corpses, and hermit crabs, which use gastropod shells to protect their bodies. 15 Gila woodpecker and Saguaro cacti Hermit crabs and gastropod shells


TYPES OF COMMENSALISM Phoresy This takes place when one organism attaches to another organism specifically for the purpose of gaining transportation . exclusively for Examples: Arthropods, of which are mites on insects (such as beetles, flies or bees), pseudoscorpions on mammals or beetles, and millipedes on birds. 16 Seed spreading


17 Mutualism


Mutualism Mutualistic Symbiosis is an interspecific interaction between two species that benefits both members. Individuals interact physically, or even live within the body of the other mutualist. Frequently, the relationship is essential for the survival of at least one member. Populations of each species grow, survive and/or reproduce at a higher rate in the presence of the other species. Mutualisms are widespread in nature, and occur among many different types of organisms. 18

“Biological barter”:

“Biological barter” 19 Resource- resource Relationships: trophic mutualism Resource-resource interactions, in which one type of resource is traded for a different resource, are probably the most common form of mutualism. Examples: Mycorrhizal associations, Rhizobia bacteria

“Biological barter”:

“Biological barter” 20 Resource- service Relationships Pollination- dispersive mutualism Phagophiles –defensive mutualism Zoochory Bee and flower Oxpecker (a kind of bird) and rhinoceros or zebra  Leafhoppers ( Eurymela fenestrata ) and ants( Iridomyrmex purpureus ) Geum Bur

“Biological barter”:

“Biological barter” 21 Service- service Relationships Ocellaris clownfish and Ritteri sea anemones Goby fish and shrimp

Facultative vs. Obligate Mutualisms:

Obligate mutualisms are essential for the survival of one or both species. 22 Facultative vs. Obligate Mutualisms Lichens Yucca moth and yucca plant

Facultative vs. Obligate Mutualisms:

Facultative vs. Obligate Mutualisms Facultative Mutualisms are not essential for the survival of either species. Individuals of each species engage in mutualism when the other species is present. 23 Rhizobacteria Bees and flower

Think and tell :

Think and tell Flowering plants and pollinators. Parasitoid wasps and polydna viruses Ants and aphids. Termites and endosymbiotic protozoa. Humans and domestic animals 24

Importance of mutualism:

Symbiotic mutualists within animal tissues Ungulates (such as Bovines) and bacteria within their intestines Termites and bacteria within their gut 25 Importance of mutualism

Importance of mutualism:

Biodiversity Sustainability 26 Importance of mutualism


Kinds of Predation Feeding Strategy Diet Example Frugivores Fruit Monkey Folivores Leaves Koalas Nectarivores Nectar Humming Bird Granivores Seeds Parrot Palynivores Pollen Bees Mucivores Plant fluids, i.e. sap Aphids Xylophages Wood Termites Importance of mutualism Seed dispersal

Mutualism plays a key part in ecology. :

Coevolution 28 Mutualism plays a key part in ecology.


29 Altruism


Altruism Altruism refers to an individual acting in a way that will decrease its own survival chances, but improve the survival chances of another individual. The Darwinian perspective emphasising ‘ survival of the fittest’ gave the impression that selfishness was the norm. Pioneering work involving the study of animals living in social groups in fact revealed that co-operation and altruism are just as ‘natural’ as selfishness. If co-operation and altruism have evolved, then they must have some adaptive benefits, researchers have analysed the conditions under which adaptations for engaging in such behaviour can be expected to evolve. Altruistic behavior can be explained by inclusive fitness – the total effect an individual has on proliferating its genes by producing its own offspring and by providing aid that enables close relatives to produce offspring.

Examples of Animal Altruism.:

Examples of Animal Altruism. Vampire bats will regurgitate and feed blood that they have collected from their prey to a hungry conspecific ( Wilkinson, 1990 ). Ground squirrels will warn others of the presence of a predator, even though making such a call may draw the attention of the predator to itself ( Sherman, 1977 ). In many species of social insects, workers forgo reproduction entirely (they are sterile) in order to help raise their sisters ( Wilson, 1971 ).


In naked mole rat populations, nonreproductive individuals may sacrifice their lives protecting the reproductive individuals from predators. Examples of Animal Altruism.

Theories of Altruism.:

Theories of Altruism . 1. Kin Selection (Proposed by Hamilton, 1964 ). By helping relatives to reproduce (even at the cost to your own reproductive success) then your shared genes can spread. Assisting a close relative thereby increases one’s ‘ Inclusive Fitness’ . Using mathematical modelling, Hamilton showed that an altruistic gene can spread through the population if it causes an individual to help a relative, whenever the cost to the individual is offset by the reproductive benefit gained by the receiver. ‘Hamilton’s Rule’ = r B>c where r =coefficient of relatedness, B = benefit to the recipient, c = cost to the giver.

Hamilton’s Rule and Kin Selection:

Hamilton ’ s Rule and Kin Selection The three key variables in an altruistic act are: The benefit to the recipient. The cost to the altruist. The coefficient of relatedness.

Hamilton’s Rule and Kin Selection:

Hamilton ’ s Rule and Kin Selection The coefficient of relatedness is the probability that two relatives may share the same genes.

Hamilton’s Rule and Kin Selection:

Hamilton ’ s Rule and Kin Selection In honey bees, most of the females in a colony do not reproduce. Female workers can increase their overall fitness by caring for sisters rather than reproducing on their own.

Hamilton’s Rule and Kin Selection:

Hamilton ’ s Rule and Kin Selection Natural selection favors altruism when the benefit (B) to the recipient multiplied by the coefficient of relatedness (r) exceeds the cost (C) to the altruist. rB > C This inequality is called Hamilton ’ s rule . Kin selection is natural selection that favors this kind of altruistic behavior by enhancing reproductive success of relatives.

Kin selection in action:

Kin selection in action An example of kin selection and altruism is the warning behavior observed in Belding ’ s ground squirrels. Ground squirrels do not give an alarm call every time a predator approaches. They only do so when there is a large proportion of their relatives within earshot ( Sherman, 1977 ). Vampire bats are much more likely to share their food with relatives than with non-relatives ( Wilkinson, 1990 ). This theory explained the most puzzling phenomena - that of the sterile insects - by a genetic quirk they are more related to their sisters than to their mothers or daughters ( Trivers & Hare, 1976 ).

Kin Recognition.:

Kin Recognition. It is important to be able to recognise kin, as the costs involved in mistaking another individuals offspring for one’s own are high, and the benefits few. Offspring recognition should evolve more often in colonial species, as there is a high risk of misdirecting parental care. Examples . Bank swallows (colonial) do not accept strange chicks whereas rough-winged swallows (solitary) do. Herring gulls (colonial ground-nesting) recognise offspring and refuse strange chicks, but Kittiwakes (colonial cliff-nesting) do not recognise offspring and accept substitute offspring.

Kin Recognition in Gulls. :

Kin Recognition in Gulls. Data from Alcock, 1993

Kin Selection in Humans.:

Kin Selection in Humans. Studies amongst diverse human populations consistently support the existence of kin selection, some examples (cited in Barrett et al., 2002 ) are as follows: Food sharing is more common amongst close relatives. Political alliances between kin are more stable than those formed between distantly related, or unrelated individuals and involve less preconditions. The passing on of wealth to lineal descendants (excluding spouses) is far more common than giving to less closely related or unrelated individuals. Close relatives are preferentially sought out in times of need and such help is less likely to be reciprocal. Relatives typically receive more expensive presents.

How Much Pain Will You Suffer For Your Kin?:

How Much Pain Will You Suffer For Your Kin? In an interesting experiment Fieldman et al., (cited in Barrett et al., 2002) asked participants to maintain a painful position. The longer they held the position the more money they would earn. In different conditions participants could earn money for individuals differing in relatedness: Themselves. Parent or sibling. Grandparent / niece / nephew, a cousin. Unrelated friend. The duration of maintaining the painful position varied as a direct proportion of relatedness, with more pain being sustained for closer relatives.

Facial Similarity and Trust?:

Facial Similarity and Trust? DeBruine (2002) argued that animals should be sensitive to cues of genetic relatedness when making altruistic decisions. In humans such decisions may be based around facial appearance. Participants played a computerised game of trust in which they had to decide whether or not to share money with an individual. They were shown faces of their 'opponents' which were either facially different to themselves, or whose faces had been morphed to resemble their own. Participants showed significantly more 'trusting' behaviour when playing against opponents that resembled themselves.

Human Adoption. :

Human Adoption . The adoption of unrelated children has been cited as evidence against kin selection as helping to rear unrelated children will not produce genetic benefits to the ‘giver’. However, Silk (1990) observed that among Polynesian cultures, a substantial number of adopters cared for children who were cousin equivalents or closer. Families who had adopted children that were unrelated tended to be agricultural families needing extra help. Similarly, in Chicago Stack (1974) reported that the majority of foster children were adopted by kin. Adopting unrelated children is a recent Western phenomenon. Alcock (1993) argues that the urge to produce children and look after them is so beneficial in reproductive terms that it has become deeply ingrained.

Problems for Kin Selection.:

Problems for Kin Selection. Kin selection does not explain observed incidences of animals helping non-relatives for example: Unrelated chimpanzees come to one another’s aid when threatened (de Waal & Luttrell, 1988). Vampire bats will feed non-relatives (Wilkinson, 1990). Humans often engage in apparently altruistic acts such as: Giving blood. Donating to charity. Forgoing reproduction. Rescuing unrelated individuals (and even animals). Sacrificing their lives for moral or ethical principles.

Reciprocal Altruism:

Reciprocal Altruism Altruistic behavior toward unrelated individuals can be adaptive if the aided individual returns the favor in the future. Proposed by Trivers (1971). Natural Selection may create psychological mechanisms designed to deliver benefits even to non-relatives, provided that such actions lead to reciprocal beneficial actions in the future. ‘ you scratch my back… ’. This is not necessarily limited to the same species e.g. cleaner fish. If the benefit received is larger than the cost incurred, then individuals who engage in such behaviour will out-reproduce those who do not. Eg, in vampire bats, an individual will share food with a conspecific (whether related or not) if the other has shared food with that individual in the past ( Wilkinson, 1990 ).

Conditions Under Which Reciprocation Flourishes. :

Conditions Under Which Reciprocation Flourishes. 1 . Individuals must associate for long-enough periods of time to develop reciprocal interactions. 2 . The likelihood of one individual performing some social exchange with another should be predicted on the basis of their past associations. 3 . The roles of giver and receiver should reverse at least once. 4 . The short-term benefits to the recipient are greater than the costs to the donor. 5 . Givers should be able to recognise and expel cheaters from the system.


Symbiosis is a relationship where two or more species live in direct and intimate contact with one another. It includes: 1. Parasitism 2. Mutualism 3. Commensalism Symbiosis 48

authorStream Live Help