Defensive Strategies in Biology

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Questions and Answers

What is a characteristic of macroparasites?

They reproduce rapidly.

They often have complex life cycles. (correct)

They are directly transmitted between hosts.

They generally cause severe morbidity.

Which factor influences the morbidity related to macroparasites?

The direct transmission rate between hosts.

The speed of reproduction.

The number of parasites carried by the host. (correct)

The immune response strength.

What type of organisms have been noted to have immune defences?

Only animals possess immune responses.

Plants have no form of immune defence.

Only mammals have advanced immune systems.

Bacteria have developed immune mechanisms. (correct)

What could be considered a basic type of defence in animals and plants?

Structural features like spines and thorns. Signup and view all the answers

What is the role of CRISPR-Cas9 in bacterial immune defence?

It snips out parts of invading viral nucleic acid. Signup and view all the answers

How many people die from snakebite in Sub-Saharan Africa each year?

30,000 Signup and view all the answers

What is Fav-Afrique primarily used for?

Neutralizing snake venom from 10 different species Signup and view all the answers

Why is the production of Fav-Afrique in jeopardy?

Manufacturer's inability to remain economically viable Signup and view all the answers

What do warning colors in aposematic organisms typically indicate?

Unpalatability or toxicity Signup and view all the answers

Which type of mimicry involves unpalatable species imitating each other?

Mullerian mimicry Signup and view all the answers

What is the primary principle behind the need for defensive strategies in living organisms?

Organisms must defend themselves to survive and reproduce. Signup and view all the answers

Which of the following is NOT considered a basic defense strategy of plants and animals?

Social behavior Signup and view all the answers

What does the term 'Lifetime Reproductive Success' (LRS) specifically refer to?

The total number of offspring produced and raised by an individual. Signup and view all the answers

Which group of organisms must defend themselves against predators, herbivores, and parasites?

Animals, plants, and bacteria Signup and view all the answers

Which concept emphasizes the relative ability of an individual to survive and reproduce within a population?

Biological Fitness Signup and view all the answers

What is one way that defensive strategies can be classified?

By the type of response required Signup and view all the answers

Which of the following statements regarding parasites and pathogens is correct?

Pathogens cause diseases to hosts after infection. Signup and view all the answers

Which strategy is emphasized as being part of the elaborate immune response of organisms?

Innate immunity Signup and view all the answers

What type of plant defense is termed 'constitutive'?

Defenses that are always present in the plant Signup and view all the answers

Which compound is not categorized as a constitutive defense?

Volatile Organic Compounds Signup and view all the answers

What defines a substance as a venom?

A toxic substance introduced by a bite causing mechanical damage. Signup and view all the answers

What is the role of allelopathic chemicals in plant interactions?

To inhibit the growth and reproduction of other organisms Signup and view all the answers

Which type of venom is primarily neurotoxic?

Cobra venom Signup and view all the answers

What does BVOC stand for in the context of plant defenses?

Biogenic volatile organic compounds Signup and view all the answers

Which of the following animals is known for producing bufotoxin?

Cane Toad Signup and view all the answers

What is the estimated number of snake bites per year globally?

5,000,000 Signup and view all the answers

What type of plant is associated with mutualism involving ants?

Bullhorn Acacia Signup and view all the answers

Which family is known for its haemotoxic venom?

Viperidae Signup and view all the answers

What percentage of snake species are believed to be venomous?

15% to 20% Signup and view all the answers

What is a key feature of inductive plant defenses?

They can be triggered by herbivore attacks Signup and view all the answers

What effect do secondary metabolites generally have on insect herbivores?

They repel or deter herbivores Signup and view all the answers

What common misconception exists about snakebite symptoms?

Ill effects may not show for 10+ hours. Signup and view all the answers

What is a characteristic feature of the Mulga or King Brown Snake?

No antivenom available for its bites. Signup and view all the answers

Which of the following statements about snakebite mortality is incorrect?

Snake bites pose no significant public health threat. Signup and view all the answers

What type of mimicry involves a harmless species mimicking a harmful species to deceive predators?

Batesian Mimicry Signup and view all the answers

Which of the following is NOT a characteristic of Müllerian mimicry?

Involves a harmless mimic Signup and view all the answers

Which of the following is a central theme of mimicry in evolution?

It may overlap with camouflage strategies Signup and view all the answers

Which of the following insects is mentioned as an example of Batesian mimicry?

Hover Fly Signup and view all the answers

Which term describes the strategy of a predator not detecting the presence of its prey until it is too late?

Crypsis Signup and view all the answers

What is the main advantage of Müllerian mimicry for both species involved?

Enhanced warning signal Signup and view all the answers

Which of the following best describes camouflage?

A strategy to blend in with surroundings to avoid detection Signup and view all the answers

Which organism is an example of Batesian mimicry in the snake category?

King Snake Signup and view all the answers

Study Notes

Defensive Strategies-1

Animals, plants, and even bacteria must defend themselves to survive and reproduce.
Defensive strategies are diverse, including camouflage, poisons, venoms, and various physical adaptations.

Primary Principle

The primary principle behind defensive strategies is that organisms need to protect themselves from predators, herbivores, and parasites (pathogens).
Parasites live on or in other organisms for part of their life cycle.
Pathogens cause diseases in the host after infecting it.

Defensive Strategies Continued

Camouflage is a strategy used by many organisms to blend in with their surroundings, helping them avoid detection.
Highly venomous bites, such as those from the Gaboon Viper (Bitis japonica), are effective defense mechanisms.
Some animals, like skunks, use foul-smelling secretions as a defense.
Other animals, like the Fulmar petrel, use projectile regurgitation as defense.
Structural adaptations, such as spines on hedgehogs and porcupines, are also used for defense.
Some animals use poison glands for defense.

Lectures Overview

The lectures cover basic defenses in plants and animals.
Poisons and venoms are discussed as defensive mechanisms.
Mimicry, a strategy of using resemblance to another organism for protection, is a topic of the lectures.
Immune system defenses, innate immunity, and the adaptive immune response are also part of the lecture material.
Epidemiology, R0, herd immunity, and novel pathogens are included.

Outline of Issues

Evolutionary context is important for understanding defenses.
Biological fitness refers to the relative ability of an individual to survive and reproduce within a population.
Darwin emphasized survival, but neo-Darwinism (modern synthesis) – from 1930 onward – places greater emphasis on reproductive output.
Lifetime Reproductive Success (LRS) is an important measure of evolutionary success.

Predators and Parasites

Predators and parasites significantly affect Lifetime Reproductive Success (LRS) and fitness.
Plants and animals, including bacteria, must defend against predators and parasites.
Parasites are organisms that at least part of their life cycle is on/in another organism.
Pathogens are organisms that cause disease to the host after infection.
Defense can be physical, chemical, and/or behavioral.

Clutch Size and LRS

Lifetime Reproductive Success (LRS) is determined by counting eggs and tracking offspring survival.

Parasites and Predators Continued

Parasites are typically smaller than their hosts, and have a shorter life expectancy.
Many parasites infect only one or a few hosts in their lifetime; rarely do they kill.
Parasites are categorized as Micro and Macro forms partially based on immune response.
Predators are typically larger than their prey and have a longer life expectancy.
Predators often attack many different prey in their lifetime.
Predators typically kill their prey.

Relationship Between Survival and Reproductive Success

Correlation data shows a relationship between survival and reproductive success.

Mosquitoes

Specifically, Aedes aegypti mosquitoes act as vectors for various diseases, including yellow fever.
They also transmit malaria, a parasitic disease that causes high mortality among humans.

Micro-pathogens (Micro-parasites)

Micro-pathogens, also called micro-parasites, have a very small size and quick replication within their hosts.
They cause severe morbidity and mortality in large numbers of people.
Micro-pathogens are commonly viruses, bacteria, and protozoa.

Viruses

There are different characteristics of viruses, including whether they are enveloped or non-enveloped.
Examples of families of viruses include herpesviridae, cornavidae, retroviridae, etc.

Influenza Viruses

Influenza viruses have different types (A, B, and C) and subtypes.
The taxonomy and classification of influenza viruses are based on their surface antigens (HA and NA).
The genome is segmented.
Their structure is enveloped, and potentially pleomorphic ranging from spheres to extremely long filaments with helical capsid.

Macroparasites

Macroparasites are large in size and do not directly and quickly reproduce within their host.
They do not typically cause severe morbidity or high mortality in their hosts, however the number of parasites present may cause a health burden.
Complex life cycles are common, and frequently involve multiple intermediate hosts.
Examples include worms, ticks, lice, bed bugs, and various types of flys.

Ticks, Lyme Disease, Rabies, and Roundworms

Ticks can transmit Lyme disease.
Rabies is a virus that can infect foxes and be fatal.
There are different types of worms (Roundworms & Tapeworms).

Points to note

Both attack and defense can be expensive in terms of energy allocation.
Defense benefits should outweigh the cost of defense.
Plants and animals invest in various defense mechanisms.
Defenses can be physical, chemical, and cellular.

Basic Defenses-1

Bacteria also have "immune" defenses.
One discovered recently is CRISPR-Cas9.
Cas9 is an enzyme that snips out parts of invading viral nucleic acid.
This enzyme acts against phages (viruses that infect bacteria).

Basic Defenses-1 (Animals and Plants)

Structural defenses include spines, thorns, trichomes, modified skin (e.g., hedgehog, porcupine).
Other defenses include fowl smells (e.g., skunk, fulmar petrel) and poison (e.g., salamander).

Plant Defenses

Plants are immobile but are attacked by herbivores.
The interaction between plants and herbivores dominates terrestrial environments.
Constitutive and inductive defenses are common in plants.

Plant Defenses Continued

Constitutive defenses are preformed chemical defenses, like alkaloids and terpenes, that are always present in the plant.
Inductive defenses are triggered in response to an attack.
These defenses can involve volatile organic compounds summoned by the plant.

Constitutive Compounds

These include alkaloids like Curare, Atropine, Cocaine, Strychnine, and Nicotine.
These compounds negatively affect insect grazers.

Inductive Compounds

These are volatile organic compounds (VOCs) and are released in response to plant damage or herbivore presence.
Biogenic VOCs (BVOC) also contribute to defense.
Herbivore-Induced Plant Volatiles (HIPVs) are summoned by herbivores to deter them or attract their enemies.
Allelopathy refers to chemicals released by one organism that impact an other organism's growth and reproduction (positive or negative).

Physical and Chemical Defenses in Plants

Various physical and chemical defenses work together in plants.

Poisons

Poisons are compounds that are produced or sequestered by animals.
Examples include cane toads, which produce bufotoxin, resulting in toxicity to predators.
Amphibians, puffer fish, and other organisms also produce toxic substances.

Venoms

Venom is a toxic substance delivered via a bite, often causing mechanical damage.
Venom is commonly used in prey capture.
Examples of venoms are those from snakes (cobra, pit viper, mamba), spiders, scorpions, and other organisms.

Aposematic Colouration

Aposematic coloration is a warning strategy used by animals with unpalatable or poisonous substances.
Bright colors and patterns are used to signal danger to potential predators.

Mimicry

Two main types of mimicry are Mullerian and Batesian.
Mullerian mimicry involves multiple unpalatable species developing similar warning signals.
Batesian mimicry involves a harmless species adopting the warning signals of a harmful one to deceive predators.
Mimicry can be complex and controversial and may overlap with camouflage.

Camouflage and Crypsis

Camouflage and crypsis are defensive strategies that allow animals to blend in with their surroundings.
These strategies help to avoid detection by predators or for ambush hunting by offensively using camouflage.

Summary-1

Different defensive strategies exist in various organisms.
Plant defenses can be constitutive (always present) or induced (in response to attack).
Animals use various defense mechanisms, including venom, poisons, and camouflage.

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Description

Explore the various defensive mechanisms organisms employ against macroparasites and other threats. This quiz covers concepts like immune defenses, mimicry, and the implications of snakebite fatalities in Sub-Saharan Africa. Test your understanding of the essential strategies in both plants and animals.