PLANTS AND ANIMALS

Biological Rhythm

Biological Rhythm

Internal and external cycles

Circadian Rhythm

An approximate daily biological rhythm (the free running cycle of about a day) which could be diurnal, nocturnal or crepuscular.

Circannual Rhythm

A biological rhythm of which the cycle takes approximately a year.

Circatidal Rhythm

A biological rhythm of which the cycle occurs approximately twice daily.

Circalunar Rhythm

A biological rhythm of which the cycle takes approximately a month.

Photoperiodism

Plant response to changes in night length

Photoperiod

Length of light compared to dark in a 24 hour period

Long Day Plant

A plant which flowers when the photoperiod is longer than the critical day length (short night).

Short Day Plant

A plant which flowers when the photoperiod is shorter than the critical day length (long night).

Day Neutral Plant

A plant whose flowering is unaffected by the photoperiod.

Phytochrome and 2 types

A pigment that detects night length. There are 2 types of phytochrome: phytochrome red (P_R) and phytochrome far red (P_FR).

What happens to P_R during the day?

P_R is quickly converted to P_FR during the day

What happens to P_FR in the night?

P_FR is slowly converted to P_R in the night

Why is it important for plants to flower at a certain time of day?

It maximises successful reproduction. Plants need their seeds germinated when the chance of survival is highest and when pollinators are most active.

What is the purpose of phytochrome concentrations?

To trigger or inhibit flowering depending on the concentration.

What is the amount of P_FR present a measure of?

The night length/photoperiod

Exogenous Rhythm

Rhythms which occur in the external environment

Endogenous Rhythm

Rhythms which occur internally through an internal/biological clock, and can continue without external stimuli present in the environment.

What drives an endogenous rhythm?

An increase or decrease of biological factors such as hormones, or melatonin which is controlled by the SCN in the hypothalamus.

Free Running Period

The length of time it takes for an endogenous rhythm to repeat in the absence of external cues.

Zeitgeber

An external or environmental cue which resets (entrains) an endogenous biological clock.

What is the purpose of a zeitgeber?

To synchronise an organism’s biological clock with the external environment.

Entrainment

When the endogenous biological clock of an organism is reset to synchronise with the environment.

Phase Shifting

When the time of activity or inactivity is pushed forwards or backwards.

Actogram

A graph showing the activity patterns of an organism over a 24 hour period, as well as changes in the environmental rhythms which may have an impact on the organism’s activity.

How to calculate the free running period

Hours shifted/days = ____ hours per day

____ hours per day x 60 minutes = ____ minutes

Free running period = 24 ± ____ minutes

Tropism

A directional growth response of a plant towards or away from a stimulus. Can be positive or negative.

What is the importance of a tropism?

It allows plants to grow towards necessary stimuli and away from harmful stimuli.

Nastic Response

A non-directional movement response of a plant.

What stimuli can cause tropisms and nastic responses?

Light (photo), chemicals (chemo), water (hydro), temperature (thermo), touch (thigmo).

Auxin

The hormone in plants which causes the responses.

What does auxin do to plant cells?

It causes them to elongate (get longer) on the shaded side, making that side grow more. It causes the growth of the stem towards the light.

What does auxin do to roots?

It prevents roots from elongating by moving to the lowest part of the roots due to gravity. The loss of auxin on the higher side causes the cells to elongate, while the cells on the lower side remain the same. As a result, the root bends and grows downwards.

Taxis

A directional movement response of animals towards or away from a stimulus. Can be positive or negative.

What stimuli can cause taxis responses?

Light, chemicals, gravity, temperature, water, touch

Kinesis

Non-directional movement response of animals where the rate of movement or activity is influenced by external stimuli.

Orthokinesis

The change in speed of an animal’s movement, where movement is faster in unfavourable conditions but slower in favourable conditions.

Klinokinesis

A change in the rate of turning (change of direction of movement) of an organism, where turning is faster in unfavourable conditions and slower in favourable conditions.

Homing

The ability of an animal to find its way home over unfamiliar areas, often after migrating to different locations.

What are some ways that homing occurs?

Animals can locate their homes through observation of landmarks, use of scent trails, and solar or magnetic compasses.

Migration

Regular, seasonal or annual mass movement of a population from breeding area to another area and back again.

How do animals know when to migrate?

External and internal factors. Migration can be triggered by changes in day length or climate, but the internal clock may prepare an animal for it.

What are the advantages of migration?

Movement to more resources, a place to give birth to offspring, away from harmful weather conditions and potential predators.

What are the disadvantages of migration?

High energy expenditure, potential to get lost or injured, risk of death.

Territory

An area where an animal lives and that it defends from other animals.

Home range

The area where an animal will search for food and water which isn’t available in their territory.

Lek

A region/area where males come together and perform mating displays, often competitively, to attract female mates for the purpose of breeding.

Ecological Niche

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

Gause’s Law

No 2 species will occupy the same ecological niche and coexist indefinitely; competition will always ensure one species survives over the other.

What will happen if 2 species occupy the same niche?

One species will have a slight advantage, and the other would face extinction or undergo a change in ecological niche.

Intraspecific Relationship

Relationships between members of the same species.

Competition

Interactions between organisms or a species in the same ecological niche for limited resources, such as space, food and mates, which will be fought over.

What are the advantages of living in a group?

Safety in numbers, being able to warn off or fight predators, help each other find food, defend territories, help to raise young, bring animals in closer proximity to potential mates.

What are the disadvantages of living in a group?

Increased competition for food and space, increased vulnerability to predators as larger groups are more noticeable.

Hierarchy

A ranking system within a population with the strongest and most dominant members at the top, and the weakest and most submissive members at the bottom.

Linear Hierarchy

(Pecking order) a simple progression from most dominant to most submissive.

Complex Hierarchy

Structures involving different groups such as subordinate groups, family groups, bonding pairs, and labour groups, often all controlled by an alpha or dominant member.

Why are hierarchies good in animal populations?

They reduce fighting and competition for resources, because submissive members know they have to wait for dominant members to eat first.

How are hierarchies maintained?

Displays where the dominant animal looks bigger while the submissive animal looks non-threatening.

Monogamy

Having one partner for the whole mating season and sometimes for life.

Polygamy

One organism has multiple mates.

Polygyny

When one male has multiple female mates

Polyandry

When one female has multiple male mates

Polygynandry

When both the male and female have multiple partners each.

Why is monogamy more useful for K-strategists?

In some environments it might take the energy of both parents to raise an offspring.

Why is polygamy more useful for R-strategists?

In some environments energy to raise offspring isn’t required and it may be more important to produce many offspring.

K strategists

Organisms that have a low number of offspring. Parents care for these offspring, resulting in them being more likely to survive to adulthood.

What are the advantages of being a K-strategist?

Offspring are more likely to survive and obtain skills from their parents.

What are the disadvantages of being a K-strategist?

More energy is used to protect and feed the offspring.

R strategists

Organisms that have a high number of offspring. Parents don’t care for their young, resulting in only a handful surviving.

What are the advantages of being an R-strategist?

Less energy is spent caring for offspring.

What are the disadvantages of being an R-strategist?

Offspring are more likely to die from factors such as starvation and predators.

Courtship

All the different actions animals take to attract a mate. Usually the male has to attract the females, and the females choose them based on their performance.

What are the advantages of courtship rituals?

The strongest and fittest males pass on their successful alleles to future generations, maintaining a healthy population.

What are the disadvantages of courtship rituals?

Some males can get injured, and often courtship rituals can attract predators.

What are some examples of courtship rituals?

Songs, dances, physical appearance, and fights with other males.

Interspecific Relationship

Relationships between members of different species.

How can interspecific competition be caused?

Members of different species competing for certain resources within the same ecological niche.

Exploitation

The relationship between two different species where one species is harmed and the other species is benefited; one species benefits at the expense of another.

What are the 3 types of exploitation?

Predation, herbivory, parasitism

Predation

Where one animal hunts and feeds on another.

Herbivory

Where an animal species feeds on a plant species.

Parasitism

Where one organism (the parasite) lives on or inside another species (the host).

Mutualism

The relationship between 2 different species where both species benefit from each other.

Commensalism

The relationship between 2 different species where one species is benefited and the other is unaffected.

Mimicry

When one species resembles another in some way. This can include mimicking appearance, behaviour, sound or smell.

Batesian Mimicry

When a harmless species mimics a dangerous or poisonous one. This ensures predators will avoid them, meaning this form of mimicry acts to protect the species from predators.

Mullerian Mimicry

When 2 unpalatable species (animals that don’t taste good) mimic each other’s warning signals. This means that if a predator learns not to eat one species, it won’t eat both as long as they look like the same species.