biology level 3 - studytime nz · 2019. 7. 18. · annual rhythms, also called circannual rhythms,...

NCEA | Walkthrough GuideLevel 3BIOLOGY

PLANT AND ANIMAL RESPONSES

Introduction 3

Orientation in Time 4

Biological Rhythms 4Circadian Rhythms 4Circannual Rhythms 5Circatidal Rhythms 6Circalunar Rhythms 7Photoperiodism 8Exogenous Rhythms 10Endogenous Rhythms 11Zeitgebers and Entrainment 12Actograms 14

Orientation in Space 16

Orientation Responses Shown by Plants 17Auxin 19Orientation Responses Shown by Animals 20Homing and Navigation 22Migration 23

Interspecific and Intraspecific Relationships 26

Territory 26Ecological Niche 27Intraspecific Relationships 28Hierarchies 30Reproductive Strategies 31R and K Strategy 33Courtship 34Interspecific Relationships 35Exploitation 36Mutualism and Commensalism 38Mimicry 38

Key Terms 42

Level 3 Biology | Plant and Animal Responses Walkthrough Guide

Level 3 Biology - Plant and Animal Responses | © Inspiration Education Limited 2017. All rights reserved.3

INTRODUCTIONThis standard is all about plants and animals.

Level 3 Biology: Plant and Animal Responses is all about understanding what animals and plants do in their environment, why they do the things they do, and how they do it.

What will you learn in this walkthrough guide?

This external topic can be split broadly into:

Orientation in time – where we look at the activity cycles of animals. Orientation in space – where we look at how plants and animals find the best place to live. Interspecific and intraspecific relationships – where we consider how different organisms interact with each other.

Within these broad topics we’ll look at biological rhythms, photoperiodism, movement responses in animals, growth responses in plants, and migration. The relationships we’ll be looking at include things like competition, predation, herbivory, parasitism, mutualism and commensalism.

A word on exam strategy.

The key to this external topic isn’t just to memorise a whole bunch of facts or definitions. It’s about being able to link these ideas to natural selection and thinking “what advantages and disadvantages will this have for the organism”. Ultimately, biology is centred around evolution and so you need to think about how everything affects the organism’s chances of reproduction and survival.

Here at StudyTime, we’re pretty much GCs (good citizens), so to help you out, we’ve made this guide in plain English as much as we can. We’ve also included a glossary for some of the key terms that you’ll need to master for your exam.

However, the language we use isn’t always something you can directly write in yourexam. When this is the case, we offer a more scientific definition or explanation (in ahandy blue box) underneath. These boxes are trickier to understand on your first read through, but contain language you are allowed to write in your exam. Look out for them to make sure you stay on target.

4 Level 3 Biology - Plant and Animal Responses | © Inspiration Education Limited 2017. All rights reserved.

Level 3 Biology | Plant and Animal Responses

ORIENTATION IN TIMEWe’ll kick off this Walkthrough Guide by looking at biological rhythms; when animals are active and inactive. It seems basic at first but we’ll begin to consider what drives these rhythms and how they can be observed in lab settings.

By the end of this section you should be familiar with a few things including:

The different types of biological rhythms: their length and what they are linked to. Photoperiodism in plants - describing when different plants flower and why. Back to looking at biological rhythms more broadly, we’ll compare rhythms that are driven by the environment and those driven by a ‘biological clock’ inside the organism. Next, we’ll see how the internally- and externally-driven rhythms are kept in-sync in the real world. Lastly, you’ll need to be able to interpret actograms – graphs which show an animal’s activity and inactivity – and be able to calculate a few things like the length of the rhythm.

Biological Rhythms

Animals are quite predictable, with many of their activities occurring at regular time periods. These are rhythmic activities and these types of biological rhythms are linked to stuff in the environment.

The idea in the exam is that you might be given a scenario and you need to identify the biological rhythm, identify what environmental changes the rhythm might be linked to – such as changes in light, day lengths or tides – and give the survival advantages to the rhythm.

Circadian Rhythms:

The easiest one to begin with is the daily rhythm

This has the mysterious-sounding name: circadian rhythms – nothing to do with cicadas.

‘Circa’ actually means approximately.

These daily rhythms have an approximate length of 24 hours and are linked to the day-night cycle.



Noon

Midnight

Best co-ordination

Highest blood pressureDeepest sleep

Humans have a circadian rhythm

For example, we wake up during the daytime and sleep during the nighttime, and we start the cycle all over again the next day. Not only this, but actual physiological things, like body temperature, show daily changes. Being active during the day and inactive at night is what we call ‘diurnal’.

Other organisms may be active at night and inactive during the day (nocturnal) or active at sunrise and sunset (crepuscular).

All of these circadian rhythms are triggered by light availability.

Diurnal Nocturnal Crepuscular

STOP AND CHECK:

Turn your book over and see if you can remember:

The length of a circadian rhythm. What might the circadian rhythm be linked to, or triggered by. Some examples of circadian rhythms.

Try to explain it in your own words.

Circannual Rhythms:

While our first biological rhythm was in-tune with the sun, our next is linked to the seasons.

Annual rhythms, also called circannual rhythms, have a length of 365-ish days.



This is the time it takes for the Earth to orbit the sun. We get our seasons – summer, autumn, winter and spring – due to the orbit of the Earth around the sun as well as the axial tilt of the planet.

What about some examples of circannual rhythms?

Some examples of circannual rhythms are the migration and hibernation of animals at certain times in the year, or when leaves fall off plants.

One of the things that changes with the seasons is the day length, and so these circannual activities are triggered by changes in day length.

6STOP AND CHECK:


The length of a circannual rhythm. What the circannual rhythm is linked to, or triggered by. Some examples of circannual rhythms.


Circatidal Rhythms:

Looking at the name, especially at “-tidal”, you might guess that this has something to do with the tides – you’d be on the right track.

So, how long are these rhythms?

Tidal rhythms (circatidal rhythms), are linked to changes in the tides and have an approximate length of 12 hours.

Only certain organisms seem to have circatidal rhythms



Many organisms living in the tidal zones will become active when the tide is high (or when the tide is in) and will become inactive when the tide is low (or when the tide is out).

When the tide is in, and the organisms are submerged underwater, this is the time for feeding and reproduction. When the tide is out the organisms are exposed to air and threatened by drying out (also called desiccation if you want to show off that you know your biology) so activity stops.

Tide out Tide in

Believe it or not the changes in tides are caused by the gravitational pull of the moon on the Earth. The pull creates the tides, while the rise and fall of tides is caused by Earth’s rotation relative to the moon.

STOP AND CHECK:


The length of a circatidal rhythm. What the circatidal rhythm is linked to, or triggered by. Some examples of circatidal rhythms.


Circalunar Rhythms:

Our last biological rhythm is not very common in the animal world but is important to consider for completeness.

Lunar, or circalunar, rhythms have an approximate length of 29.5 days.

Or we can call it around about a month. These circalunar rhythms are linked to the orbit of the moon around the Earth. Sometimes we see a full moon, no moon or a crescent moon, and this all just depends on how the Sun is shining on it.



How about some examples?

It’s a bit dodgy to talk about werewolves in a biology guide, but they’re a great example of having a circalunar rhythm. Every full moon, an ordinary-looking citizen transforms into a wild beast; a werewolf.

The time it takes for another full moon to occur is 29.5 days as the moon needs to come back to the same position relative to the Sun and Earth.

Therefore, the transformation of werewolves has a circalunar rhythm.

STOP AND CHECK:


The length of a circalunar rhythm. What the circalunar rhythm is linked to, or triggered by.

Try explain it in your own words.

Photoperiodism

Now let’s not forget about plants

Photoperiodism is the regulation of seasonal activities by the day length, which is also called the photoperiod.

Basically, photoperiodism is about when plants flower depending on the day length.

Plants can be classified into a few different types:

Long-day plants, like sunflowers, only flower when the day length exceeds a particular day length – the critical day length. These plants flower during summer.



Short-day plants, like spinach, only flower when the day length is less than its particular critical day length. These plants flower during winter. Day-neutral plants, like tomato plants, are not affected by the day length and can flower any time in the year.

SHORT DAYPLANT

Day length

LONG DAYPLANT

This photoperiodism response is controlled by phytochrome.

Phytochrome is a type of plant pigment.

Phytochrome has two forms:

Pr or Pred Pfr or Pfar red

During the day, there is a whole bunch of red light which is absorbed by Pred and converted to Pfar red. At night time, when there is more “far red” light, Pfar red is converted back into Pr. The levels of Pred and Pfar red basically tells the plant when to flower.

Red light

Pr Pfr

Dark Reversion

Far - Red light

Long-day plants flower when the day is long enough so that enough Pfar red builds up.Short-day plants flower when the day is short and the night is long so that there is more Pred.



But why does it matter to plants when they flower?

It’s all about reproduction!

Plants want their seeds to germinate at the same time every year at a time when the chance of survival is highest. If the flowers are pollinated by insects then flowering would need to occur when the insects are most active.

STOP AND CHECK:


What time of the year long-day, short-day and day-neutral plants flower. The role of pigments in photoperiodism.


Exogenous Rhythms

So, we’ve established that most organisms – both animals and plants – have some kind of biological rhythm.

Different activities in the organism can range from having short circatidal rhythms to long circannual rhythms. The length of the cycle is the period.

Turns out that these rhythms can either be:

Externally driven – these are exogenous rhythms. Internally driven – these are endogenous rhythms.

Let’s kick off with exogenous rhythms which are more straightforward

Whenever you see “exo-“ always think “outside”

In this case, exogenous means “outside the body”.

So, exogenous rhythms are controlled by something outside the body – they are externally driven.

This something is the environment – in other words, exogenous rhythms are those that are driven by changes in the environment.



We’ve actually already talked about the things that might control an exogenous rhythm

These are the things like light availability in a day-night cycle, tide length in a circatidal rhythm, or the changing day length in circannual rhythms.

Exogenous Rhythms

6

One thing to keep in mind is that there aren’t many rhythms controlled only by the environment – many are driven by an internal clock as well as changes in the environment.

What is this internal clock we speak of?

You’ll find out in the next section…

STOP AND CHECK:


The two types of biological rhythms. The definition of an exogenous rhythm. What types of things might ‘drive’ an exogenous rhythm.


Endogenous Rhythms

While “exogenous” means “outside the body”, “endogenous” means “inside the body”

Endogenous rhythms are internally driven by an internal clock – often called a biological clock.



Deep in the brain there’s a little clock – so deep you can’t hear its “tick-tock” – that regulates the rhythms of activities.

For those crazy about biology, the biological clock is the suprachiasmatic nucleus in the hypothalamus of the brain. (BUT YOU DON'T NEED TO KNOW THIS!)

Sleep Now

So, how do endogenous rhythms differ from exogenous rhythms?

Well, because they are controlled by a biological clock they are not affected by changes in the environment and can continue when the environmental conditions remain constant.

When a biological rhythm is running during constant environmental conditions the rhythm is said to be “free-running”.

For example, the biological clock controls the production of cortisol and melatonin which do a whole bunch of things when at different levels, such as make us feel tired.

STOP AND CHECK:


How endogenous rhythms differ from exogenous rhythms. What on Earth a “free-running” period is. What drives the endogenous rhythm.


Zeitgebers and Entrainment

The sleep-awake cycle of humans is controlled by both an internal clock and the environment – let’s ignore pesky alarm clocks.

The internal clock makes us feel tired, so we sleep, because the body needs to do certain things while we’re awake and when we sleep.

If we were wild animals, we’d need to be up during the day when the sun is up and then sleep during the night when the sun is gone. That’s because we rely on our eyes to see and we need the light to find food.



The problem is that the internal clock in humans is more than the 24-hour day-night cycle.

It’s closer to 25 hours.

Often the endogenous rhythms in organisms are not the same length as the same cycle in the environment.

Therefore, there needs to be a way to keep things in-sync.

This act of resetting the internal, biological clock to match the environment is known as entrainment.

But, what actually forces the cycles to remain in-sync?

Zeitgebers are environmental cues that reset an internal clock.

These can be anything from light, temperature, humidity, just any environmental factor you can think of.

For example, a common zeitgeber for circadian rhythms is sunrise or sunset (light availability): this resets the internal clock so that activity always starts at the beginning of the day.

Reset your clock

When an internal clock is entrained, phase-shifting occurs.

Phase-shifting is when the time of activity or inactivity is pushed forwards or backwards.

STOP AND CHECK:


Why biological rhythms need to be “reset”. The purpose of zeitgebers. Some common examples of zeitgebers out there. What entrainment means. What is meant by the term “phase-shifting”.




Actograms

The Plant and Animal Responses external requires you to analyse actograms.

An actogram is a graph showing when an organism is active and inactive over the course of each day, as well as any changes in the environment.

Using actograms, we can figure out whether a rhythm is endogenous or exogenous, the length of the biological rhythm (period), and any entrainment and phase-shifting that occurs.

Have a look at the simple actogram below:

Entrained toZeitgeber

Free-running

The dark lines show periods of activity (and each line is a new day), and if we look at the top half we can see that this animal is active at night and inactive during the day. The top half of the actogram shows when the animal is exposed to normal environmental conditions. The bottom half of the actogram shows when the animal is exposed to constant environmental conditions with the removal of light. We can see that even without light the animal becomes active and inactive. Therefore, there is an endogenous biological rhythm controlled by the biological clock. Looking at the bottom half of the actogram again we can see that it becomes active later and later each day. This is because the endogenous rhythm is not exactly 24 hours.The reason that the cycle of activity and inactivity starts and stops at the same time each day is because the animal is entrained with a zeitgeber (light, in this case) which resets the endogenous rhythm and keeps it in-sync with the environment.



Actograms can also be used to determine the length of the biological rhythm

This means you can say whether it’s circadian, circannual, circatidal, and so on.

Days

External time

0

0 6 12 18 0 6 12 18 24

4

8

The lines of activity start at the same time each day (approximately 18 hours from time 0 – so 6pm) and stops at the same time (approximately 6 hours from time 0 – so 6am). Therefore, the biological rhythm has a length of 24 hours and is a circadian rhythm. The length of activity time is 12 hours (6pm to 6am) and the inactivity time is 12 hours (6am to 6pm).

What about phase-shifting?

If entrainment was occurring you could determine the amount of phase-shifting by seeing how much later or earlier the activity started each day during the free-running period.

This would also allow you to determine the length of the endogenous rhythm.

STOP AND CHECK:


The purpose of actograms. What is shown on an actogram. How to determine the length of the biological rhythm using an actogram.




Quick Questions

Consider the actogram below:

Light Light

Days

Hours0

7

14

21

0

0 24 48Dark Dark

Dark

This shows the physical activity of a mouse over a 4-week period, where the dark bars show when the mouse decided to run inside a rotating wheel. In the first 2 weeks, it was exposed to 12 hours of light and then 12 hours of darkness, but in the 3rd and 4th week the darkness was maintained.

What is the rhythm shown by the mouse in the first two weeks? Define the free-running period, and explain where it is being shown in this actogram.

Define entrainment, and explain when it is occurring here. How is entrainment achieved?

Why does the start time of the mouse’s activity change each day during the 3rd and 4th weeks? What is this process called?

ORIENTATION IN SPACESimple orientation responses are those that occur in response to environmental factors, such as light, temperature or chemicals.

Essentially, these responses act to move the animal from an area of unfavourable conditions to an area of favourable conditions, or make the plant grow towards favourable conditions and away from unfavourable ones.

?



So, here's the plan:

We’ll kick off by looking at the two orientation responses in plants: tropisms and nastic responses.

After that we’ll look at how a small molecule, auxin, helps the plant carry out these growth responses.

Switch things around and we’ll do the same for animals: taxis and kinesis. Keeping with our animals we’ll discuss more complex orientation responses,

including homing, navigation and migration. What’s the point to all of these and how do they occur?

Orientation Responses Shown by Plants

Life is good for animals: when it’s too hot we can move into a cool spot, when we get wet we can go somewhere to dry off, and if we’re starving we can walk into the kitchen and grab a snack. Life isn’t as easy for plants…

The one crucial thing they’re lacking is movement.

But evolution gave them a saving grace: tropisms and nastic responses.

Let’s start with tropisms

Tropisms are directional responses to a directional external stimulus.

What this means is that the plant grows – it doesn’t move – towards or away from a stimulus.

If they grow towards a stimulus we’ve got ourselves a positive tropism.But if they grow away from a stimulus it’s a negative tropism.

shoot grows in the direction of sunlight

So, what kind of stimuli are involved?

There’s a handful of things actually, with plants growing in response to light, chemicals,



gravity, water or physical contact (touch).

We can give each specific tropism a name based on the stimulus:

When the stimulus is light it is a phototropism. Chemotropism when the stimulus is a chemical.You can use either gravitropism or geotropism when the stimulus is gravity. When the stimulus is water it is a hydrotropism.Thermotropism - temperature stimuliFinally, thigmotropism is the funky name when the stimulus is physical contact or touch.

Negativelygeotropic

Positively geotropic

Tropisms are very important as they keep plants alive

This is because they can grow towards the good stuff and grow away from stuff that might kill them.

Plants need light and water for photosynthesis so they’ll usually have a positive phototropism and positive hydrotropism.

But they might want to grow away from dangerous chemicals so will have a negative chemotropism. Some plants will grow towards touch – like when vines wrap around structures – while others will grow away.

A similar thing in plants is the nastic responses

Unlike with tropisms, direction is not important here. That’s because nastic responses are non-directional responses to the intensity of the stimulus. They aren’t always growth movements.



A photonasty could be flowers opening up during the day and closing at night.

STOP AND CHECK:


The difference between tropisms and nastic responses. The difference between a positive and a negative tropism. The possible stimuli that plants respond to, including the specific names we use for them.


Auxin

We talked a lot about plants growing in response to different environmental factors, like light, water, gravity, chemicals and touch.

But how does this growth occur?

It’s not like the plants see light and will tell themselves to grow towards it, and they certainly can’t smell dangerous chemicals and back away.

Instead there’s a handy little plant hormone called auxin that does the job.

Wait, hormones?

Hormones are molecules that are often produced in one location and do stuff in another.

Auxin is produced in the tips of plant shoots and cause cells to grow longer than normal.

When thinking about phototropism, the plant bends and grows towards a light source

When the plant shoot is exposed to light, auxin diffuses down the dark side of the plant.

Therefore, the cells on the dark side grow longer – they elongate – while the cells on the light side stay the same. As a result, the plant shoot bends towards the light.



Auxin released ondark side of shoot

Area of cellelogation

PlantShoot

Normal size cells

Shoot growstowards sunlight

Things get a bit strange in the roots because auxin has the opposite effect

Auxin prevents roots from elongating.

With gravitotropism/geotropism the plant roots grow downwards.

What happens is that auxin moves to the lowest side of the roots due to gravity, and the loss of auxin on the higher side causes cells to elongate while the cells on the lower side stay the same. The result is that the root starts to bend and grow downwards.

STOP AND CHECK:


The definition of a hormone. The role of auxin in phototropisms. The role of auxin in gravitropisms/geotropisms.


Orientation Responses Shown by Animals

We had a look at growth responses in plants – tropisms and nastic responses – now we flip things around and look at movement responses in animals.

The equivalent of tropisms is a taxis response

A taxis response is a directional response involving the movement of the animal either towards or away from the directional external stimulus.

The only difference between tropisms and taxes is that tropisms are a growth response



in plants, while a taxis response is a movement response in animals.

Just like with tropisms you can have positive and negative taxes: moving towards a stimulus (positive taxes) or moving away from a stimulus (negative taxes). We can give specific names to the responses based on the external stimulus: phototaxis (stimulus is light), chemotaxis (stimulus is a chemical), gravitaxis/geotaxis (stimulus is gravity), thermotaxis (stimulus is heat/temperature), and thigmotaxis (stimulus is physical contact, or touch).

The second type of orientation response in animals is a kinesis

A kinesis is a non-directional response where the rate of movement or activity is influenced by the external stimulus.

There are two types of kinesis responses:

Orthokinesis:

Orthokinesis involves a change in the speed of an animal’s movement, where the movement is faster in unfavourable conditions but slower in favourable conditions.

For example, woodlice move slower when it’s really humid.

Klinokinesis:

Klinokinesis involves a change in the rate of turning of an organism. The rate of turning is faster in unfavourable conditions but slower in favourable conditions.

For example, flatworms turn more often when there is more light so that it ends up spending more time in the dark.



Orthokinesis Klinokinesis

STOP AND CHECK:


The difference between orientation responses in plants and in animals. The difference between orthokinesis and klinokinesis. The definition of a taxis response.


Homing and Navigation

So far, we’ve looked at more simplistic orientation responses in animals where they move in response to nearby stimuli that get their attention.

In this section and the next, we’ll consider complex orientation responses over long distances – homing and migration – which are influenced by the internal biological clock as well as environmental factors.

The first one is homing.

Homing involves an animal finding its way “home” over unfamiliar areas, often after migrating to different locations.

The problem is, without opposable thumbs and the necessary intelligence, Google Maps is too advanced for them to use. Instead, homing requires other kinds of navigation, which relies on the environment in one way or another.



The most obvious kind of navigation involves using landmarks to guide their way

These have to be permanent landmarks like rivers, mountains, valleys, or even man-made things like roads. Related is the use of scent trails, often used by certain lizards like salamanders.

More fascinating animals use solar or magnetic compasses

So, they might find their way using the direction of the sun (solar compass) or even the direction of Earth’s magnetic field lines (magnetic compass).

The magnetic compass is commonly used by birds and how they do it is a tad complicated to explain here – just know that it exists!

Not only can they use the Sun to guide them, but they might use the patterns of the stars at night.

STOP AND CHECK:


What homing is. How animals find their way back home.


Migration

Homing is all about coming back to their normal home after going on a type of getaway. What’s really important to drill into your head is that migration isn’t just packing up randomly and going to a new destination, it is this regular movement of whole populations to a specified location.



Migration is the routine movement to the same place over and over and over again.

So, why bother packing up and leaving anyway?

Migration is always undertaken so that the population can move to a more favourable location – favourable in terms of climate and/or habitat – for the population’s survival.

Here’s one reason:

One typical reason involves groups of animals moving to a new feeding ground at certain times of the year because their usual home runs out of food during the winter.

Here's another reason:

The other main reason is for either breeding or for giving birth to offspring. Sometimes their usual home, or territory, is not ideal to give birth to young due to factors like predators, different food sources or harmful weather.

So, they would travel to a location that’s more beneficial for their offspring.

But, how does an animal know when it’s time?

We said that migration is a regular movement which means it happens at specific times in the year. From all the yarns we spun about biological rhythms, you might guess that migration relies on both external and internal factors.

Migration will often be triggered by changes in day length or changes in climate, but the internal clock might prepare the animal for migration.

There will also be some preparation involved:

It would be awful silly for an animal to just start flying away without some kind of planning involved. Migration requires preparation, such as increasing fat layers to increase energy supplies for the long journey ahead, or in birds, losing feathers and replacing them with lighter ones to maximise flight efficiency.



STOP AND CHECK:


The definition of migration – try to be specific. The possible reasons an animal might decide to migrate elsewhere.


Quick Questions

The Arctic tern has the longest distance migration of any bird. It breeds in the Arctic during the summer where the climate is more temperate and then travels to the Antarctic where it has its non-breeding areas. By travelling between hemispheres, it ends up seeing two summers every year.

Using the example above, define migration. Using the example above, explain the purpose of migration and the advantages it brings. Why might the Arctic tern want to travel to the Antarctic?

Discuss possible ways the Arctic tern knows when it’s time to migrate. What are some possible ways the Arctic tern uses to find its way between the Arctic and Antarctic?

Wheat shoots, also called coleoptiles, show a response to a directional light source: Name the specific response this involves. Explain the mechanism used to produce this response. Hint: think of a specific plant hormone.

Explain why this response would be useful to plants.

Consider the two examples of animal behaviour below:

The movement of woodlice depends on the humidity, with an increase in humidity leading to an increase in the time that the woodlice will remain stationary.

The movement of the flatworm depends on the light intensity, with increasing light leading to the flatworm turning more.

Identify the responses shown in each of the two examples, and explain the reasoning for your choice.

The examples show non-directional responses. What are directional movement responses called? How do they differ from the responses shown by these two examples?

Using the two examples above, why are these movement responses useful for the animal?

?



INTERSPECIFIC AND INTRASPECIFIC RELATIONSHIPSThis last section looks at how animals, plants and even microbes interact with other species. There’s lots of different concepts to cover.

By the end of this section you should be confident with:

Territories, home ranges and leks: the differences between them and the purpose of each. Ecological niche and Gause’s Law. Interactions between members of the same species (intraspecific relationships), which includes competition, hierarchies, reproductive strategies and courtship behaviour. Interactions between members of different species (interspecific relationships). Here we’ll cover exploitation, mutualism, commensalism and mimicry.

Territory

Let’s kick off with territories

A territory is the area where an animal lives and the area that it defends from other animals.

Part of the defence is a boundary, often identified by scent (so other animals know they should really back off), with animals patrolling at the boundary.

A good example is where meerkats stand guard as look-outs on a high rock at the boundary of their territory.

Extending on from the territory is the home range

The home range is the area where an animal will search for food and water that it can’t find in its territory.

Unlike the territory, the home range isn’t defended so animals are vulnerable to predators here.



Home range of A

Zone of overlap

Home range of B

Territory of BTerritory of A

The last type of “area” important to animals is a lek

A lek is where males (usually) come together and perform mating displays, often competitively, to attract female mates for the purpose of breeding.

The advantage is that it becomes a hotspot for breeding, increasing the success of mating, but the disadvantage is that while they’re busy getting busy they’re all vulnerable to predators.

STOP AND CHECK:


The difference between a territory, home range and a lek.


Ecological Niche

The animal’s home, or territory, is just one part of the overall picture.

The ecological niche doesn’t just look at where the animal lives, but looks at things like its food source, any predators or prey, how, when and where it reproduces, the interactions it has with other species, and how it survives in its environment.

We can condense all of these factors into a simpler definition

The ecological niche is the physical and biological conditions or factors a population/species faces in its habitat.

It’s just important to remember the ecological niche doesn’t just tell us where the



animal lives.

The important concept involving ecological niches is the competitive exclusion principle – sometimes called Gause’s Law

It basically says that no two species can co-exist within the same ecological niche.

If you have two species living in the same location, eating the same food, feeding on the same prey, and so on, they will compete for these resources.

Species A

Interspecificcompetition

Species B

Ultimately, one species will have at least a slight advantage over the other and this species will dominate while the other species will either face extinction or will undergo a change in ecological niche.

But two species with the exact same ecological niche will not co-exist indefinitely.

STOP AND CHECK:


The definition of an ecological niche – what kinds of things does it consider? What would happen if two animals had the same ecological niche.


Intraspecific Relationships

Part of an animal’s ecological niche is its interactions with other animals. These interactions can be with other species or can be with other animals from the same species.

Think of an international flight – it is between two different countries. An interspecific relationship is an interaction between two different species. The opposite of “inter-“ is “intra-“, so intraspecific relationships are interactions with other animals from the same species.



INTRASPECIFIC INTERSPECIFIC

Part of intraspecific relationships include territories – which we’ve already covered – and reproductive strategies and hierarchies that we’ll cover next.

A common intraspecific relationship is competition.

Since members of the same species have the same ecological niche, things like space, food and mates will often be fought over.

One of the consequences of intraspecific competition is aggressive behaviour and fighting.

This is important for the strongest, most dominant members to get the best resources.

The downside is that the animals can get injured or even die, so instead, fighting tends to be ritualistic being a show of strength rather than a fight to the death.



Members of the same species often live together in groups

There are a few advantages and disadvantages to this intraspecific relationship:

The advantage is that there is safety in numbers, being able to warn or fight off predators. They can also help each other to find food, to defend territories, or even help to raise young. Being in groups brings potential mates in closer proximity. The downside is that disease is more common in close groups, there is competition for things like food and space, and there can even be increased vulnerability to predators as large groups are more noticeable.

STOP AND CHECK:


What an intraspecific relationship is. Examples of things that animals may compete over. The advantages and disadvantages of living in groups.


Hierarchies

We touched upon the idea that members of the same species often live together in groups which often leads to competition which then leads to aggressive behaviour and fighting.

One thing that is put in place to reduce fighting is a hierarchy

A hierarchy in a population is a ranking system, with the strongest and most dominant members on top and the weakest, most submissive members at the bottom of the ranking.

These hierarchies are formed by members competing for rank and can be changed as new members take over spots.

Linear hierarchies – or pecking orders – involve a simple progression from most dominant to most submissive.Complex hierarchies are structures involving different groups such as subordinate groups, family groups, bonding pairs, and labour groups, often all controlled by a dominant, alpha member.



Pecking order

Dominant

Submissive

Complex hierarchy

Hierarchies are very good to have in animal populations

By establishing rank, each member knows its place in the hierarchy which reduces fighting and competition for food and other resources.

This is because the submissive members know they will have to wait for the dominant members to eat first.

The positions are maintained by display where a dominant display makes the animal look bigger (standing tall, holding tails up high, exposing teeth, fluffing up feathers, and so on), while a submissive display involves trying to look non-threatening (lowering head, avoiding eye contact, tucking tail between the legs, or even rolling over to expose vulnerable body parts).

STOP AND CHECK:


The difference between linear and complex hierarchies. The purpose of establishing hierarchies.


Reproductive Strategies

The other major aspect of the ecological niche is reproduction.

If we keep things basic, animals that sexually reproduce do one of two things:

1. Make a whole load of offspring with a few managing to survive and grow up. 2. Make just a few offspring with most of them surviving and becoming adults.



We can also think of reproduction in terms of partners

Either species find a mate and stick with them, at least for the one breeding season. Birds, for example, are well-known for having one partner for the mating season, with some even mating for life.

The opposite is polygamy where one individual has multiple mates. This can involve a male having multiple female mates (polygyny), a female having multiple male males (polyandry), or both males and females having multiple partners (polygynandry).

PolygamyMonogamy

Compared to monogamy, polygamy in a population tends to increase the genetic diversity.

Monogamy or polygamy being the norm in a population depends on the environment essentially

Emperor penguins often have long-term monogamous relationships because it takes full commitment of both parents to raise a child in the harsh Antarctic environment. In other species, it doesn’t really matter and all the parents have to do is either deposit their sperm or lay the eggs. Therefore, polygamy might be more beneficial.

STOP AND CHECK:


The difference between monogamy and polygamy. The kind of situations where monogamy would be more useful. The kinds of situations where polygamy would be more useful.




R and K Strategy

R-strategists are the ones that have high numbers of offspring – fish are an excellent example

This is because the parents don’t care for the young, and so by having lots and lots of babies, chances are that at least a handful will survive and carry on the population.

The pros are that the parents only need to put in a low amount of energy per offspring and the parent’s survival isn’t jeopardised by looking after offspring.

The downside is that many of the offspring will die of starvation or will be eaten by predators.

R-strategy

The opposite is K-strategists, which include primates, who decided to have a low number of offspring

These K-strategy parents spend a lot of time and energy on each offspring, raising them and bringing them to adulthood – this is the downside. They need to look after them, feed them and protect them from evil, while preparing them for the big, bad world.

The advantage is that the offspring are much more likely to survive.

K-strategy

So, what’s the difference between these offspring?

K-strategy babies tend to be more helpless and less developed than R-strategy babies.



That’s because as soon as R-strategy babies burst into life they’re on their own. K-strategy babies have the easy life and can rely on their parents – human babies rely on their parents for like 18 years.

STOP AND CHECK:


The pros and cons of the R strategy for reproduction. The pros and cons of the K strategy for reproduction.


Courtship

Reproduction is so important that we have a third section on it! We talked about whether species are monogamous or polygamous, as well as talking about whether they have millions of babies or just a couple.

But, how do they actually find a mate to do all of this reproduction nonsense?

Finding a mate is called courting, while courtship describes all the different things animals do to attract a mate.

Most of the time in the animal kingdom it’s up to the male to attract the female, and the female chooses them based on their performance.

There’s a whole bunch of courtship rituals

These can include songs, dances, fights with other males, or simply just appearance.

The advantage of spending all this time fluffing about finding a mate is that the strongest or fittest males are the ones who pass on their alleles, maintaining a fit and healthy population.



The downside is that sometimes courtship is a dangerous period of time: some males get hurt or injured, and often the rituals can attract predators.

For example, a male peacock’s colourful display is great for attracting the ladies but it makes them super obvious to predators. Similarly, singing really makes you stand out, both to potential mates and predators – it gives away your position.

STOP AND CHECK:


Some examples of courtship rituals that might be used by animals.


Interspecific Relationships

Now that we’ve looked at the types of interactions between members of the same species, let’s change gears and look at the interactions between different species.

We’ll look at each type in more depth in the next few sections and it’s important that you can explain whether the species are benefiting, harmed or are not affected by the relationship.

The first lot of interactions comes under the broad title of exploitation.

Exploitation includes predation, herbivory and parasitism. In all of these cases one species benefits and the expense of the other species.

It’s not all doom and gloom because some species have evolved partnerships where they either work together (mutualism) or one species benefits with no effect to the other (commensalism).



Interaction Species A Species B

Commensalism Receives benefit Not affected

Mutualism Receives benefit Receives benefit

Parasitism Receives benefit Harmed

Not only that, but we can have interspecific competition.

This is similar to intraspecific competition. However, it involves different species fighting for a shared food source or a shared space/territory.

Just like with intraspecific competition, interspecific competition results in aggressive behaviours and fighting, the difference being that it is more likely they will fight to the death.

A common example is lions and hyenas who share the same geographical location, hunt the same prey and scavenge the same meat. This results in fighting between the two species, with each species killing the young of the other.

STOP AND CHECK:


The names of the interspecific relationships where one species benefits while the other is harmed.

The two interspecific relationships where neither species is harmed. The similarities and differences between interspecific and intraspecific competition.


Exploitation

To keep it simple, exploitation is the relationship between two different species where one species benefits while the other is harmed – one species benefits at the expense of the other.

Predation is where one animal hunts and feeds on another

Just to make sure we’re on the same page, the one that gets to eat benefits while the one that dies and gets eaten is harmed.



Herbivory is a type of predation, which involves one animal species feeding on a plant species.

Again, the one eating gets the benefits, whilst the plant species is harmed – hey, plants have feelings too! The plant is harmed because the population or the plant decreases in size.

The last example of exploitation is parasitism

Parasitism involves one organism, called the parasite, living on or inside another species, which is called the host.

Unlike predators, parasites don’t want to kill their host. Instead, they benefit by having a secure home for reproduction or by taking some of the host’s resources, like food, water and heat. The host is harmed because it simply has less resources.

In humans, parasites are things like head lice and tapeworms.



STOP AND CHECK:


The similarities and differences between predation and herbivory. How a parasite might benefit from the host. Examples of parasitism.


Mutualism and Commensalism

Interspecific relationships don’t just involve species being harmed.

Mutualism:

Mutualism is the relationship between two different species', where both species benefit – they help one another out. (When members of the same species help each other out this is called cooperation).

Mutualism can involve doing jobs, or services for each other, or one species does a job in return for resources, like food or space.

In humans, we have gut bacteria that help us digest food. We provide them with a place to live and let them snack off the food that passes through the intestines, and they pay us in good digestion and development of a gut immune system.

Commensalism:

Commensalism is slightly different in that it is the relationship between two different species where one benefits while the other is unaffected. The benefit usually comes from the supply of food, shelter or transport, and usually involves a large host and a small commensal (the one benefiting).

A common example is where birds feed on the insects found on the backs of mammals, like elephants. The birds are getting all of the invertebrate goodness while the elephant goes about its daily business.

STOP AND CHECK:


The difference between mutualism and commensalism. Some ways that a species might benefit from a mutualistic relationship.



Mimicry

One sneaky way of avoiding predators is mimicry, where one species resembles another in some way. It could be mimicking appearance, behaviour, sounds or even smells.

One type of mimicry is Batesian mimicry

Batesian mimicry is where a harmless species mimics a dangerous, or poisonous, one.

Predators will see the mimic and think “oh no, these are those poisonous animals that make me sick” and then back off.

Viceroy butterfly(The mimic - palatable species)

Monarch butterfly(The model - distasteful species)

Therefore, Batesian mimicry protects the species against predators.

The other main type of mimicry is Müllerian mimicry.

Müllerian mimicry is where two unpalatable species (animals that aren’t tasty) mimic each other’s warning signals.

If you have two unpalatable species that don’t resemble one another, a predator will try to eat one species, find out they taste gross, and then move on to taste the second species.

What would be more beneficial to both species is that they look like each other, so that when the predator learns not to eat one species it effectively learns not to eat both since they look the same to the predator.



STOP AND CHECK:


The purpose of mimicry. The definition of Batesian mimicry. What Müllerian mimicry is and how it differs from Batesian mimicry.


Quick Questions

Consider the 3 examples of interspecific relationships below:

Vitamin B12 is an important vitamin that makes sure the brain and nervous system are functioning normally and that the red blood cells are made properly. However, humans can’t make it and there are no fungi, plants or animals that are able to make it, so there are no food sources with B12 for us to eat. Only lactic acid bacteria inside our guts are able to make it. In return, our guts provide nutrients and space for these bacteria to live and grow.

Demodex folliculorum is a mite that lives on the face of almost every single human being. These microscopic animals feed off the dead skin cells and the oils that are excreted from hair follicles and skin glands. As far as we know, these mites do not provide any benefit to us.

?



Plasmodium is a group of protozoa which cause malaria in humans. Infected mosquitos transfer the protozoa when they bite someone. Plasmodium enters the bloodstream and use the red blood cells to replicate and grow. Once they’ve finished the red blood cells are burst open and destroyed, and the protozoa are picked up when another mosquito comes along and bites a human.

Identify the type of interspecific relationship occurring in each of the examples above, and explain your choices.

Using the examples above, explain the difference between mutualism, commensalism and parasitism.

Explain how co-evolution can occur because of interspecific relationships.



KEY TERMSAuxin:

A plant hormone which elongates cells in the shoots of plants but causes cells to not elongate in the roots.

Batesian Mimicry: A form of mimicry where a harmless species resembles a dangerous of unpala-table one.

Circadian Rhythm: A biological rhythm linked to the day-night cycle with a length of approximately 24 hours.

Circalunar Rhythms: A biological rhythm with a length of approximately 29.5 days.

Circannual Rhythm: A biological rhythm linked to the seasons, or changes in day length, with a length of approximately 365 days.

Circatidal Rhythms: A biological rhythm linked to changes in tide – high tide and low tide – with a length of approximately 12 hours.

Commensalism: An interspecific relationship where one species benefits while the other is unaffected.

Competitive Exclusion Principle: (Also called Gause’s Law), the law that states that no two species can co-exist with the exact same ecological niche.

Courtship: The different things animals do to attract a mate.

Day-neutral Plants: Plants which flower all year round and are not affected by the day length.

Ecological Niche: The physical and biological conditions or factors a population faces in its habitat.



Endogenous Rhythms: Biological rhythms which are driven by an internal biological clock.

Entrainment: The act of resetting the internal biological clock to match the environment.

Exogenous Rhythms: Biological rhythms which are driven by external, environmental factors.

Exploitation: An interspecific relationship where one species benefits while the other is harmed.

Free-running Period: The period of time where an animal’s biological rhythm is running under constant environmental conditions.

Herbivory: Exploitation involving an animal feeding on a plant.

Hierarchies: The ranking system that exists in populations, with the strongest members at the top and the weakest members at the bottom.

Home Range: The extended area outside the territory where animals forage for food.

Homing: The ability of an organisms to finds its way home over unfamiliar areas.

Interspecific Relationships: The interactions between two individuals from different species.

Intraspecific Relationships: The interactions between two individuals who belong to the same species.

K Strategy: The reproductive strategy where a small number of offspring are produced with a high energy input.

Kinesis: A non-directional response where the rate of movement or activity of the animal is influenced by the external, or environmental, stimulus.



Klinokinesis: The change in the rate of turning of an organism, where the rate is faster in unfavourable conditions.

Lek: The area where animals come together and perform mating displays to attract mates for breeding.

Long-day Plants: Plants which flower in the summer when the day length exceeds a critical length.

Migration: The regular movement of whole populations to a specific location.

Mimicry: Where one species resembles another is some way.

Monogamy: Having one mate for a breeding season.

Müllerian Mimicry: A form of mimicry where two unpalatable species resemble one another.

Mutualism: An interspecific relationship where both species benefit.

Nastic Response: A non-directional growth response in plants to the intensity of an external, or environmental, stimulus.

Navigation: The ability of an organism to use landmarks or natural compasses to find its way home.

Orthokinesis: The change in speed of an animal’s movement, where the movement is faster in unfavourable conditions.

Parasitism: Exploitation involving a typically smaller species (the parasite) living on or in a larger species (the host) where it steals the host’s resources.



Phase-shift: The change in the start time of activity or inactivity as a result of entrainment.

Photoperiodism: The regulation of seasonal activities of plants by the day length, or photoperiod.

Phytochrome: A type of plant pigment which has two forms – Pr and Pfr – and controls the flowering of plants.

Polygyny: Where a male has multiple female mates.

Predation: Exploitation involving an animal hunting and feeding on another.

R Strategy: The reproductive strategy where a large number of offspring are produced with a low energy input.

Short-day Plants: Plants which flower in the winter when the day length is less than a critical length.

Taxis: A directional response involving the movement of an animal towards or away from a directional external (or environmental) stimulus.

Territory: The defended area where an animal lives.

Tropism: A growth directional response in plants to a directional external (or environmental) stimulus.

Zeitgebers: Environmental stimuli which reset the internal biological clock.The ability of an organism to use landmarks or natural compasses to find its way home.

biology level 3 - studytime nz · 2019. 7. 18. · annual rhythms, also called circannual rhythms,...

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