The assessment for this standard will require students to:
1) Describe the process(es) within the following responses:
· orientation in space (tropisms, nastic responses, taxes, kineses, homing, migration)
· orientation in time (annual, daily, lunar, tidal rhythms)
· interspecific relationships (competition for resources, mutualism, exploitation including herbivory, predation, and parasitism)
· intraspecific relationships (competition for resources, territoriality, hierarchical behaviour, cooperative interactions, reproductive behaviours).
2) Explain their understanding to show:
· how the responses occur
· why the responses provide an adaptive advantage
for the organism in relation to its ecological niche.
· linking biological ideas to explain why the
responses provide an adaptive advantage for the organism in relation to its
ecological niche. This mainly involves relating how an animal or plant interacts with biotic and/or abiotic factors in their environment to be more successful.
Behaviours always relate to the 3 Fs...
FEEDING (gaining nutrition/rate of photosynthesis)
FIGHTING (reducing conflict that would result in a reduction in overall fitness or developing a defense strategy)
FOOLING AROUND (gaining access to mates/pollinators and increasing the chance of offspring surviving)
ADAPTIVE ADVANTAGE
An organism which is able to sense a particular stimulus and respond to it in a way that increases its chance of gaining nutrition, avoiding injury and living to see its genes passed on to the next generation demonstrates an adaptive advantage.
When observing entire species as a whole, behaviours that increase efficiency by saving time and energy for individuals within the group, also provide an adaptive advantage.
Adaptive behaviours are selected for when they provide a reproductive advantage.
- cooperative breeding
- courtship
- home range
- kin selection
- agonistic behavior
- auxin
- exogenous
- endogenous
- entrainment
- free running period
- zeitgeber
- photoperiodism
- phytochrome
- biological clock
- suprachiasmatic nuclei (SCN)
PLANT ORIENTATION RESPONSES
Tropisms and Nastic Responses
Enjoy the amazing power of timelapse photography to provide us a glimpse of plant movement.
This video provides an excellent overview of plant growth responses to stimuli in the environment. Observe carefully which responses are directional tropisms and which are non-directional nastic responses. Also, pay attention to where the hormone auxin is produced and how it moves throughout shoots and roots to create the desired response.
The oxalis plant is particularly sensitive and demonstrates nastic responses to blue light, white light and touch.
Morning glory exhibits both nastic responses (spiralling of the shoot tip) and tropic responses (phototropism and thigmotropism)
The video below explores Darwin's investigations into the mechanism for plant sensing, coordination and response. The conclusion of a plant hormone (auxin or IAA) being responsible for uneven elongation of plant cells was essential to predicting and understanding the response of plants to different environmental conditions.
Questions for consideration:
What conclusion could be drawn from each of the following observations?
a) the shoot with a covered coleoptile tip showed no growth toward the light.
b) unequal growth of the shoot occurred below the agar block which separated the shoot from the tip.
c) the shoot with the tip shifted to one side only showed growth on the side directly below the shoot tip.
d) the agar block showed the same response once the tip was removed.
Nastic responses are often due to changes in turgour pressure. Changing the size and shape of certain cells by adding and removing water allows for more temporary and reversible changes. Ion pumps work to concentrate K+ and Cl- ions on one side of a membrane, making it hypertonic, causing water to flow to that side of the cell membrane by osmosis.
The opening and closing of flowers, directional changes in leaves turning to follow the sun, the snapping and resetting of a venus fly trap, etc., are alll the result of nastic responses.
You may have heard about the tortoise and the hare, but have to seen the race between the snail and the mimosa plant? Who can move faster? Watch and learn about one of the thigmonastiest organisms around. What adaptive advantage does the mimosa's response provide?
PLANT BIORHYTHMS
Plants are able to sense day from night. Naturally, the zeitgeber (stimulus) in this case is sunlight in the natural environment. Sensing seasonal changes in day length, more accurately called photoperiod, allow for plants: to alter their growth rates (germination, root growth and leaf development) to take advantage of optimal environmental conditions; to avoid harm during inclimate periods (abscission = dropping leaves); and to synchronize reproduction with pollinator populations.
Seasonal temperature changes are sometimes also important in order to reset (entrain) circa-annual rhythms. For example, vernalisation is the process where dormancy is broken only following a cold period (perennial bulbs of spring flowers, flowering in fruiting trees). Photoperiod may also play a role in this process.
The phytochrome system in plants provides the mechanism by which plants measure photoperiod. It can be thought of as an equilibrium between two forms of the same phytochrome which absorbs different wavelengths of energy depending on which shape the phytochrome is in.
Pr absorbes red light to quickly transform into Pfr.
In the absence of light, or under far red light (infrared), Pfr slowly converts back into Pr.
Depending on the length of night, some or all of the Pfr may have been converted back into Pr. The ratio of Pr to Pfr in the morning is what signals plants to flower.
Long day plants flower in response to a persistant concentration of Pfr. It is likely that once a critical day length is reached and Pfr is unable to be completely converted back into Pr at night, this persistance of Pfr in the plant stimulates flowering.
Short day plants flower in response to the absence of a persistant Pfr concentration. It is likely that Pfr inhibits the flowering of short day plants. When there is a long enough night for all of the Pfr to be converted back to Pr, the inhibitory signal is lost and these plants flower. Thus, they have a critical night length. (the critical day length is the longest day after which the plant can no longer flower)
For specific examples watch this video.
This is a longer, but comprehensive videos of additional plant hormones, the mechanism for flowering in response to photoperiod for short-day and long-day plants and also defense mechanisms for plants.
ANIMAL ORIENTATION RESPONSES
TAXIS AND KINESIS
Taxis describes the intentional movement toward (+) or away (-) from a certain stimulus. A taxis response allows an organism to quickly get to a more favourable place. Examples include:
+ chemotaxis - moving toward a higher concentration of a chemical attractant. Egg cells, queen insects, fertile butterflies and a host of other organisms use chemical attractants called phermones to help themselves be more easily found.
- phototaxis - cockroaches, slaters, and many noctural animals move away from light to seek safer places where predators may not be able to find them, or where the risk of dessication is reduced.
Other taxis relate to sensing touch (thigmo),
On the smallest level, this video shows how a single white blood cell (neutrophlil)
Kinesis describes a change in rate of motion in response to a stimulus. The movement in this case is random, rather than directional, and serves to increase the chance of finding a more favourable condition. Kleinokinesis refers to a change in direction (random turning increases with increasing intensity of stimulus) whereas orthokinesis in a change in rate (moving quicker/slower as the intensity of stimulus changes).
Examples: random turning could increase the chance of finding food, or seeking shelter when too exposed. Moving quickly when in dry conditions and more slowly in dark/humid conditions favours staying in protected situations.
This video demonstrates how to investigate orientation responses in woodlice. Using a choice chamber, scientists can observe preferred behaviours of organisms. From there, we can assume they are able to sense certain abiotic and biotic factors in their environment.
HOMING
Silver ants head out of their nest at the hottest part of the day to seek food. With very few landmarks in the desert, these ants use the sun to calculate the quickest way home.
Landmarks, sun and star compasses, magnetic fields, chemical attractants and sounds including echolocation can all be used to sense and recognise home.
MIGRATION
The video below asks the question, "where do birds go in winter?" Thinking about historic ideas and scientific exploration, we know much about amazing journeys of many birds.
After watching this video, consider the following:
What preparation is needed ahead of a great migration?
How do birds time their migration?
What is the cost of migration?
What are the benefits to migrating?
How do birds find their way?
Birds are not the only animals to migrate. Check out these videos below.
Spiny lobster migration: As you watch this video consider how lobsters know where they are, which direction they are heading in, and what strategies they may have to get there safely.
Magetoreception is one method that lobsters and other animals (particularly those in the sea) use to navigate large distances. The video below explains how magnetite and crytpchromes can be used to sense the alignment of the Earth's magnetic field to migrate.
CASE STUDY 1 - MONARCHS:
The video below explains a multi-generational migration in monarch butterflies. They winter in Mexico then fly north in spring. As the north heats up, new generations fly further north taking advantage of the new arrival of spring flowers. Three generations pass before the "great-grandchildren" of the original Mexican monarchs now in Canada fly back south to Mexico. What is the adaptive advantage of this migatory behaviour?
The video above outlines several themes we have studied:
1) How do monarchs time their migration to ensure their survival?
2) How do monarchs who have never been to Mexico know which direction (orientation) to travel?
3) What is the relationship between the monarch and the milkweed?
4) What advantage is gained by this relationship?
5) What message does the video share for conservation biologists in Mexico, America and Canada?
CASE STUDY 2 - HONEY BEES
Below is a video which explains the complex communication system of bees that helps them navigate.
Before watching, pay attention to the following and write your own summary.
1) How does the bee's sun compass work on cloudy days?
2) How can bees communicate with one another the direction and distance of a valuable food source?
3) How does their internal biological clock assists them in finding sweet flowers and their way home?
INTRASPECIFIC ANIMAL BEHAVIOURS
HIERARCHIES
Hierarchies helps to define roles and responsibilitiesthat assist in cooperative living. They can help to establish a division of labour where the burdens of hunting, feeding/rearing offspring and protecting the group become shared responsibilities. Jostling for rank amongst the hierarchy can also work to determine fittness and reproductive rights so that the best combinations of alleles are passed on.
Often hierarchies are established through physical combat, size/posturing, challenges of skill or may be the result of inheritance. Play in infancy of many animals takes the form of ritualised fighting that will become useful in competing for dominance, hunting, and/or defending the group.
Rank can vary from "alpha" (dominant) to "omega" (most subordinate). Grooming and preening can be used to signal respect for higher ranked members of the group. Agonistic and submissive behaviours can be used to minimise physical conflict and reinforce rank. Growling, signposting (scratches/urination), hissing, ear/tail position, posture, calling/singing, pecking, etc. are all agonistic behaviours designed to warn challengers to stay away and know their place. Those insisting on challenging and lose, often end up leaving the group.
Subordinate members may show submissive behavours such as lowering their heads/bodies, exposing their belly/rolling over or making sounds to indicate non-threatening intentions. Subordinate members that stay within the group are often related to more dominant individuals... through kin selection, subordinate members stay and their actions favour the survival of the offspring of their siblings by assisting with hunting, parenting and protecting the group, even if they themselves never get to mate.
In the video below, take note of the considerations that the zoo keepers take ahead of introducing tiger cubs to unknown adults. How can the zoo keepers be sure the cubs will be safe if put with adults?
TERRITORIES
A territory is an area that is actively defended. This may be by physical means or various forms of agonistic behaviours (growling, singing, scent marking/urinating, scratching, etc.) designed to threaten, but reduce the risk of physical harm, illness, infection or death. Territories are usually declared for the purpose of mating/gaining access to mates and may extend to include exclusive feeding areas. Fitter animals can compete for the largest and/or most resource rich territories.
Animals may cooperatively share a common home range for feeding which is only divided into territories during the breeding season. Within the home range, safety in numbers often benefits the species.
By establishing territories, the population will be spread over a larger area which reduces competition between individuals for limited resources in one area. It is timely that this occurs at a time when population numbers increase. More importantly, the reproductive advantage for the species is that more fit individuals will be more successful at increasing the frequency of their alleles throughout the population.
Check out these leaf legged insects fighting for territories. What advantage does having a territory give these males?
Why is there an adaptive advantage for a species to show territorial behaviour?
In the video the researchers were investigating the affect of food eaten by males on their phenotype. What do you suppose they might find, and why?
LEK BREEDING SYSTEMS
In some species reproduction is enhanced by bringing everyone together, rather than spreading the population out across large distances through the establishment of territories in which young are reared. A lek is a location/arena where many males will come to for a limited time during a brief period of fertility and compete through elaborate displays, jostling for position, or the establishment of "territories" within the arena that indicate relative fitness. Physical confrontation is kept to a minimum by establishing rules of the competition and ritualised fighting is often observed.
This strategy reduces time needed to search for a mate, and more easily allows females to determine relative fitness of males. Often only a few males may end up mating with many females, thus ensuring the best combination of alleles is passed forward to the next generation. One limitation to this system is that a very successful male would be unable to care for all of his offspring, so it is observed more commonly in species that require less parental care in order for young to survive, or in highly cooperative groups relying on safety in numbers.
COURTSHIP - This can involve displays, dances, songs, gift giving, grooming, preening, shelter building or any other form of ritualised behaviour that serves to establish the following:
i) that both animals are the same species
ii) that both animals are sexually mature and fertile
iii) that the intended interaction is for mating purposes
iv) that the mate being chosen is 'fit'
Courtship displays are most elaborate and repeated over long periods of time when the formation of a strong pair bond in a species can serve to increase the likelihood of offspring surviving as a result of shared parental care responsibilities (more adults feeding/protecting the young).
Imagine life as a spider... how do you approach a female while letting her know your intentions, without being threatening, or eaten yourself?
Birds of Paradise have got to take the cake when it comes to courtship displays. This extavagance can only be the result of an environment with plentiful food resources and tough competition for mates. The males and females are extremely different (showing sexual dimorphism) and displays are elaborate to prove one's fitness and win a mate.
If you would like to see more, this video is 48 minutes, but is a great watch of some of the rarest birds.
Be sure to note the adaptation of a lek breeding strategy featuring male competition through the jostling of position and elaborate displays, and female choice (around 9 min).
Weaver birds - Courtship in some animals involves a practical display of skill that goes beyond just proving beauty or strength. How do you think the ability to build a nest relates to fitness?
The male weaver birds in the previous video must collect up to 1000 strands of grass, one at a time, and intricately weave a nest to win over a female onlooker. These males not only build a useful shelter, but throug their actions they show tenacity and stamina, exactly the same skills accosicated with collecting food for their young.
Bowerbirds - Taking next building to the next level, these artists build an attractive shelter and go through the meticulous proess of interior decoration to attract a mate. It would appear that beauty is in the eye of the beholder. In some species, a dance is also required to win over the female.
INTERSPEFIC RELATIONSHIPS
MUTUALISM
A symbiotic relationship between two species in which both species benefit.
PARASITISM
A relationship between two species in which one species benefits and one is harmed.
Defense Strategies
TIME TO TEST YOURSELF
Watch the video below and answer the questions that follow to discuss the adaptive advantages of the dolphin's behaviour and the relationships between the dolphins and the heron.
1. Dolphins live in the ocean but swim upriver to hunt during a three hour window around low tide. Explain the mechanism behind this timing response.
2. Explain the adaptive advantage of the intraspecific behaviours of the dolphins.
3. Discuss the interspecific relationships between
a) The dolphins and the fish
b) The dolphins and the heron
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