Adaptations & Diversity - AOS2 U2 - Chapter 10 - VCE Biology

Genetic Diversity

The amount of genetic variation that exists between individuals.

• Measured by reference to a population’s gene pool

Importance of high genetic diversity

Populations with a greater genetic diversity (number of alleles in gene pool) are more likely to have alleles that are already well adapted to survive new environmental challenges

 Therefore, the larger the gene pool, the greater that population's resilience to environmental change.

Disadvantages of low genetic diversity

• Reduced adaptability to adverse environmental conditions due to the lack of different alleles in a gene pool, which makes a population more likely to enter extinction

• Increased susceptibility to disease

The Theory of Natural Selection

Charles Darwin suggested that some organisms are born with favourable traits suited to the conditions of the environment. Those who lack these traits face a struggle to survive and eventually die out, however individuals who possess these advantageous traits are more likely to survive, reproduce and pass on their alleles to their offspring, leading to the evolution of s species

Framework for Natural Selection Questions (VAST SAINE)

VARIATION	Variation in phenotypes exists within populations.
STRUGGLE	A specific environmental selection pressure exists that causes a struggle for survival and reproduction.
SELECTIVE ADVANTAGE	Organisms with phenotypes that best suit the environment have a selective advantage; the best chance of survival and reproduction. Whilst organisms with phenotypes have a disadvantage; a lower chance of survival and reproduction, eventually dying out.
INHEIRTANCE	The advantageous allele is passed down from parent to offspring via DNA, leading to the expression of the advantageous trait.
EVOLUTION	Overtime, the population will become better suited to its environment, causing changes to the phenotypic frequency of a population and evolution i.e. the species evolves

Adaptation

A structural, behvaioural or physiological characteristic that enables an organism to survive and reproduce in its habitat

Structural Adaptation

Refer to the shape and structure, that is, the physical appearance of the organism

Examples of Structural Adaptations + Benefits

• Waxy cuticles on leaves - Prevent excessive water loss

• Long, slender fingers - Allowing for reach into tight crevices to access food

• Fur - Offers camouflage and insulation

Physiological Adaptations

Refer to the function of body parts and biological processes

Examples of Physiological Adaptations + Benefits

• Production of poison and venom - Provides protection from predators'

• Nectar production in plants - Attracts pollinators like bees

• Antifreeze proteins - Prevents bodily fluids from freezing in cold environments

Behavioural Adaptations

Refer to the behaviours and actions of an organism

Examples of Behavioural Adaptations + Benefits

Migration - Sustains access to food and shelter throughout different times of the year

Scent marking - Can outline territory or attract mates

Hibernation - Energy conservation in periods of low food availability

Stomata (Plant Adaptations)

Stomata are pores found on the underside of leaves.

By opening and closing stomata, plants can regulate the amount of water loss.

Plant Adaptations to Lower Water Availability

• Hard, thick waxy cuticles reduces evaporation from leaves

• Reduced number of stomata, or hair on the leaves to trap water and increase the humidity at the surface of the leaf

• Leaves roll inwards, covering stomata. When water does evaporate, it increases the humidity around the leaves, reducing future water loss.

• Cacti and succulents store water in leaves and stems

Plant Adaptations to High Temperatures

High temperatures increase water loss through evaporation.

• Leaves with a smaller surface area absorb less heat

• Plants with leaves that dangle vertically to reduce their exposure to the sun.

• Shiny leaves which reflect light and heat.

Plant Adaptations to Low Light Exposure

Plants rely on light for photosynthesis; a process that uses light energy to create glucose (food), so most adaptations occur in plants exposed to low light levels.

• Higher amounts of chlorophyll (light absorbing pigment) to capture more light.

• Water plants have large, flat, floating surfaces to absorb more light.

Plant Adaptations for Gaseous Exchange

Water plants have more difficulty than land plants in exchanging gases - Required for photosynthesis.

These plants may have stomata on surfaces other than leaves.

Mangroves have special aerial roots called pneumatophores that extend out of the water. These roots obtain oxygen for respiration through special pores located on the root.

Plant Adaptations for Increased Support

Water plants may have weaker root systems as they rely on the water for buoyancy and support.

Water plants in fast moving water have holdfasts.

Plant Adaptations to Fire

Seed Volume

• Some plants produce large numbers of seeds that only germinate (grow) after a fire.

• Advantage: Seeds have access to increased minerals from the ash in soil.

• Disadvantage: If the time between fires is too long, the seeds may not mature, and the next generation may be lost.]

Epicormic Buds

• There may be epicormic buds under the bark that sprout quickly after fire.

Plant Adaptations to Cold Climates

• Plants may have an altered chemical composition of their plasma membranes to keep the membrane fluid.

• Plants increase the concentration of solutes, like glucose, in their cells, which lowers their freezing points.

• Some plants can produce anti-freeze proteins that disrupt the formation of ice crystals in their cells.

• Deciduous trees drop their leaves during colder months.

This allows them to:

• Avoid frozen leaves

• Conserve energy and water

• Experience less branch breakage during heavy snowfall and strong winds.

General “Sun Plant” Adaptations/Features

• Large cells

• Less and smaller chloroplasts

• Small, thick leaves

• High stomatal conductance

• High photosynthetic capacity in leaves

• Low leaf area ratio

• Vertical leaf orientation

General “Shade Plant” Adaptations/Features

• Small cells

• Bigger and more chloroplasts

• Large, thin leaves

• Low stomatal conductance

• Low photosynthetic capacity in leaves

• High leaf area ratio

• Horizontal leaf orientation

Comparison of Human an Ape Bone Features

C-shaped spine	S-shaped spine
Long and narrow pelvis	Shallow and bowl-shaped pelvis
Straight femur	Femur angled towards the knees to support upper body/center of gravity
Apposable/prehensile big toe No heel or arch on foot	Big toe aligned with other toes Heel and arch present on foot

Cranial Capacity (Human Vs. Ape Skulls)

Hominins have a larger cranial (skull) capacity than apes, which is an indication of their brain size.

Apes have a cranial capacity of ~400cm³ compared to 1400cm³ in humans.

Prognathism (Human Vs. Ape Skulls)

Apes have a pronounced muzzle; their teeth protrude out from their face.

Hominins have a much flatter face.

Foramen Magnum (Human Vs. Ape Skulls)

The foramen magnum is the hole at the base of the skull where the spinal cord enters the brain.

In apes, the foramen magnum is towards the back of the skull. This supports a posture that is not fully upright.

In hominins, the foramen magnum is toward the centre of the skull at the fulcrum (balance point). This allows for bipedalism – walking on two legs.

Nuchal Area (Human Vs. Ape Skulls)

The area where the neck muscles attach onto the back of the skull to keep the skull balanced on the spine.

Apes have very large nuchal areas and associated neck muscles which allows them to keep the skull facing forward when the spine is attached further to the rear of the skull.

Temporal Muscles (Human Vs. Ape Skulls)

The muscles that pull the jaw up to bite.

These muscles are much larger in apes compared to humans.

This may have corresponded with a more primitive diet that included more fibrous plant material that needed to be ground down.

Zygomatic Arch (Human Vs. Ape Skulls)

The bony arch just behind the cheeks, providing a gap for the temporal muscles to pass through.

These are much larger in apes than in humans, to accommodate larger temporal muscles.

Brow Ridge

The bony ridge located above the eye sockets.

Apes have much larger brow ridges due to the larger strain on their skull by their temporal muscles; the ridge reinforces the weaker bones of the face.

Without the more pronounced brow ridge, their eye sockets would collapse.

One of the last traits to be lost on the path to modern humans.

Sagittal Crest (Human Vs. Ape Skulls)

A ridge of bone running lengthwise along the midline of the top of the skull.

Presence of the sagittal crest indicates that there are strong jaw muscles; the crest allows attachment of the temporal muscle.

The sagittal crest is absent/reduced in most hominins.

Mandible - Lower Jaw (Human Vs. Ape Teeth)

The lower jaw is much larger in apes, associated with a diet consisting of leaves and fibrous plants that need to be ground down.

In humans, the chin has developed to protect a weak point in our less robust skulls.

Dental Arcade - Upper Jaw (Human Vs. Ape Teeth)

The dental arcade is the shape made by the rows of teeth in the upper jaw.

Apes have a more U-shaped dental arcade, while humans have a more V/parabolic shaped one.

Diastema (Human Vs. Ape Teeth)

Apes have a gap called the diastema between the upper incisors and canines.

The gap accommodates enlarged lower canines.

Teeth (Human Vs. Ape Teeth

• Apes have much larger canines and incisors.

• Apes also have a larger grinding surface on their molars to grind food.

• In many apes, the canines are considerably larger in males compared to females; this sexual dimorphism does not exist in humans.

• Apes have thinner enamel, adapted to eating fruit, and humans have thicker enamel, adapted to chewing tougher food.

The Classification of Humans

Kingdom - Animalia

Phylum - Chordata

Class - Mammalia

Order - Primates

Family - Homindae

Genus - Homo

Species - Homo Sapiens

Classification of the Animalia Kingdom

• Multicellular organisms

• Eukaryotes without cell walls

Classification of the Chordata Phylum

• Animals with a spinal cord/backbone

Classification of the Mammalia Class

• Females have mammary glands and produce milk

• Single lower jawbone

• Hair or fur

Classification of the Primate Order

• Forward facing eyes

• 3D colour vision

• Prehensile (grasping) hands and an opposable thumb

• Large brain for body size

• Nails (not claws)

Classification of the Super Family Hominoidea*

Hominoids:

• Includes:

  • Great apes (chimpanzees, gorillas and orangutans)

  • Lesser apes (gibbons)

  • Humans

• Distinctive molar teeth

• No tail

Classification of the Family Hominidae

• Includes the great apes and humans

• Larger brains than other primates

• Flat face

• Upright posture

• Stereoscopic vision

Classification of the Hominini Tribe*

• Includes modern and extinct humans species and all our immediate ancestors

• Bipedal (walked upright)

• Reduced canine teeth

Classification of the Homo Genus

• Hominins with S-curved spines

• Recognizable as human

Classification of the Sapien Species

• Humans

• High forehead

• Well-developed chin

• Thin skull bones

Organism

A living thing that can undertake the 7 processes of life (MRS GREN)

Population

A group of organisms of the SAME SPECIES (can interbreed) living in the same area

Community

A variety of different species living and interacting in the same area

Ecosystem

Multiple communities interacting with their non-living environment in the same area, in a self-sustaining way

Components of an Ecosystem

• Abiotic factors (non-living)

• Biotic factors (living)

Biotic Factors + Examples

Living factors that affect another organism or shapes the environment

Ex. Predation, food availability, competition, disease

Abiotic Factors + Examples

Non-living factors that affect organisms

Ex. Temperature, light intensity, water, soil PH and mineral content, gases

Population Dynamics and how it can be measured

The study of changing populations over time.

• Population distribution

• Population abundance & density

• Birth, death & migration rates

Population Distribution

The geographical spread of a population at a given time.

Limited by the ideal habitat of a species and its ability to tolerate different environments

Clumped population distributions can indicate…

• Resources are clumped in the ecosystem

• Abiotic factors change throughout the ecosystem

• Behavioural adaptations in a species (eg, safety in groups/herds)

• Mating season

• Reproduction of plants (eg. Via runners)

• Only some patches of the ecosystem are suitable to live in

Uniform population distributions can indicate…

• The presence of one organism determines how close or distant another is (territorial behaviour)

• Resources are evenly spread out across ecosystem

• Abiotic conditions are suitable throughout area

Random Distributions can indicate…

• Individuals are spaced irregularly, without a predictable pattern

• Location of one organism doesn't affect the location of another

• May be linked to method of reproduction

  • Example: Dandelions have wind-dispersed seeds. The seeds spread widely and sprout where they happen to fall, as long as the environment is favourable.

Population Density (Abundance)

The number of individuals in a population in a given area

Information that can be deduced from population density

• Volume of resources in ecosystem

• Carrying capacity

• Lifestyle of population (eg. Herd, solitary. migration etc.)

• Pests and disease

• Effect of a natural event (eg. Bushfire or flood)

Population Growth Rate Equation

Population Growth = Births (B) - Deaths (D) + Immigration (I) - Emigration (E)

• A population is increasing if the birth rate and immigration rate exceed the death and emigration rate

Difference between Immigration and Emigration

Immigration - Arriving in a new place

Emigration - Leaving a place

Migration

A regular, long distance change in location

• Triggered by unsuitability in climate, availability of food or season

Carrying capacity

The maximum population size that a habitat can support in a sustained manner

The “J-shaped Curve”

When a species is introduced into a new area, it will experience an exponential growth rate (in the shape of a J) as organisms have access to and take advantage of abundant resources

The “S-shaped curve”

Eventually the growth of a population will plateau, shifting from a “j-shaped” to “s-shaped” growth curve when the carrying capacity is reached

How population density can impact population growth

Dense populations would use up the available resources in an ecosystem more quickly than less dense populations.

Density Independent Factors (Factors Affecting Density)

Factors in the environment that are unaffected as population density changes

ex. Climate

Density Dependent Factors

Factors in the environment that change with the density of a species

ex. Availability of food

• As density increases, the effect of the density-dependent factors becomes stronger

Ecological Relationships

Complex network of interactions and interdependencies between species

Symbiotic Interactions

• Mutualism

• Commensalism

• Amensalism

• Parasitism

Non-Symbiotic Interactions

• Predation

• Competition

Symbiosis

Close and long-term ecological relationship between organisms of different species

Mutualism + Example

(+/+)

A relationship between two species in which both benefit from the interaction

ex. Bees sourcing nectar from flowers whilst pollinating them

Commensalism + Example

(+/0)

Interactions between 2 organisms of different species where one gains some benefit while the other is unaffected (experiences no significant benefit or harm)

Ex. Remoras attaching themselves to sharks for a free ride

Parasitism + Example

Parasite benefits and the host is harmed

• It is not in the interest of the parasite to damage the host to the extent of killing it (needs to continue gaining resources)

Ex. Tapeworm in humans

Types of parasites

(+/-)

Ectoparasite - Lives outside the host

Endoparasite - Lives inside the host

Amensalism + Example

(0/-)

Interactions are between two organisms of different species where one organism experiences some negative effect while the other experiences neither a beneficial nor negative effect.

Ex. Algae bloom can lead to the death of many fish but do not benefit from it

Non-symbiotic Relationships

Relationships between different species who do not necessarily live close together or, the relationship is not long-term

Competition Interactions

Between two or more organisms competing for the same pool of resources

Types of competition

Intraspecific - between the same species

Interspecific - between different species

Resources which are competed for…

• Food

• Mates

• Nest Sites

• Shelter

• Water

• Light

Predation Interactions

Between different species where one organism hunts (the predator) and kills another (the prey) organism for food

The Predator-Prey Cycle (no specific order)

• Predators do not have enough prey to eat. The predators get weaker and some die

• Predator population decreases. Fewer predators hunt the prey

• Prey population increases

• Predator population has more prey to eat

• Predator population increases. More predators eat the prey

• Prey population decreases

The number of prey and predators are…

Linked

• Increase in prey numbers = corresponding following increase in predator numbers

General Predator Adaptations

• Fast

• Camouflaged

• Poisonous

• Large

• Work in groups

• Sharp claws and teeth

• Good senses (smell, sight, hearing)

• Stalking, waiting and trapping behaviour

General Prey Adaptations

• Camouflage

• Safety in numbers

• Hiding ability

• Staying still

• Lookout (vigilance)

• Mimicry

• Produce repellants

Keystone Species + Importance

Organism that helps define an entire ecosystem

• Disproportionately large effect on natural environment relative to its abundance

• Without keystone species, the ecosystem would be dramatically different or cease to exist altogether

Types of Keystone Species

• Apex predators

• Ecosystem Engineers

Apex predators + Example

Have no natural predators; sit at the top of the food chain.

• Help control the populations of prey species, which in turn affects the quality of plants and animals further along the food web

Ex.

With Keystone:

• Sharks are apex predators and feed on cownose rays

• Cownose rays feed on bivalves and arthropods

• Bivalve and arthropod populations are stable

Without Keystone

• Overfishing decimates shark population

• Cownose rays overpopulate

• Bivalve and arthropod populations collapse (later impacts cownose ray populations)

Ecosystem Engineers + Example

An organism that creates, changes or maintains a habitat

Ex.

Beavers construct dams and create wetlands where many species of fish such as salmon and trout live

Examples of Indigenous Adaptations Knowledge + Uses

Water-holding Frog: Water source when found burrowed in drought areas

Lawyer Cane Plant: Strong, flexible, useful as a fishing hook/wire saw

Stingray Barbs - Backwards pointing teeth useful for hunting and fighting

Possum fur - Insulation in cold/wet weather