ENT 104 Midterm 1

Founders of Ethology

Founders of Ethology

Konrad Lorenz, Niko Tinbergen, Karl von Frisch

Konrad Lorenz

studied imprinting and stimulus response

Niko Tinbergen

Studied stimulus response in simple reflexive behavior

early version of levels of analysis

Karl von Frisch

Waggle dance and social behavior of bees

Function of zebra stripes

disorient flies

Early ethologists thought animal behavior was ______

fixed and inflexible; instinctive

superstimulus

An exaggerated cue or stimulus to elicit an exaggerated response in the animal

central pattern generators

nerves that control stereotyped periodic behavior like walking

Reductionist approach

breaks down animal behavior into simple compartmentalized actions

Behavioral Ecology

Intersection between ecology, behavior, and evolution

maladaptive behavior

behavior that once had an evolutionary benefit but is now harmful in a novel environment

Sociobiology

the use of animal behavior knowledge applied to humans

Cons of sociobiology

much of human behavior is based on learning

human behavior is much more complex than animal behavior

current topics popular in animal behavior

social behavior (using social insects as a study)

Reproductive behavior (using birds as a study)

Why is evolutionary theory not always useful?

behavior can be maladaptive (not evolutionarily grounded; novel environments)

Behavior can be biologically based but not explainable by evolution

stimulus response models

Imprinting (ducks)

superstimulus (fish)

example of maladaptive behavior

Jewel beetle

phenotypic plasticity

when one genotype produces multiple phenotypes

phenotypes are produced in different contexts

daphnia experiment

1- collected daphnia and predatory larvae

2- collected chemicals from predatory larvae

3- raised daphnia in conditions with or without the chemical

4- daphnia raised with chemical developed spines while daphnia raised without did not

daphnia experiment takeaways

-ecological environment is critical to behavior (biotic interactions)

-early research is not always correct (correlation is not direct causation)

-simple cues can be a reliable indicator

Scientific method

- observation

- hypothesis

- experiment

- reject or fail to reject the hypothesis

- refine the hypothesis and repeat

Scientific experiment

manipulation of variables in a situation so that only one variable is different (must have control and treatment)

Inclusive fitness theory (kin selection)

genes can spread via your offspring or the offspring of a relative

relatedness asymmetries

individuals will choose to help closer relatives over more distant relatives

Worker policing

workers eating other worker eggs

single mated hypothesis (worker policing)

workers are more related to their sister’s offspring than to the queens offspring, therefore they should favor worker production of males and SHOULD NOT police

multiply mated hypothesis (worker policing)

workers are more closely related to the queen’s offspring than their sister’s offspring, therefore they should favor queen production of males and SHOULD police

Worker policing experiment (honey bees)

• honey bees should police because they are multiply mated

• inserted both queen and worker eggs into honey bee nest

• recorded rate of removal for each

• queen laid eggs removed at a much lower rate, worker laid eggs removed very quickly

confounding variables

something that cooccurs with treatment, that wasn’t controlled for

common confounding variables: age + experience; genotype + environment

Egg Confounding Variable Experiment (Ratnieks and Visscher 1989)

• worker eggs are much smaller and more misshapen

• maybe workers remove eggs because they are less viable?

• experiment: hatch eggs in incubator, preventing worker removal of eggs to test viability

• found no difference in viability

Kin selection alternative hypotheses

Kin selection: relatedness asymmetry leads workers to remove eggs

Superorganism: colony efficiency is improved if workers remove eggs

Prediction table

helps show what variables are needed to test to support a hypothesis

Superorganism experiment (worker policing)

• tested egg hatching rates in real nest instead of incubated

• queen eggs are more likely to hatch

experimental artifact

when result is dependent on artificial situation (eg incubator)

examples: in vitro vs in vivo (works in petri dish, not in animals); lab vs field

correlation not causation

pattern that matches expectation doesn’t mean it caused it

eg best male peacock is loudest, biggest, most colorful. But these traits are all associated

not mutually exclusive

all variables can be true

eg the best male peacock can be a combination of the loudest, biggest, and most colorful

Honey bee Division of labor

caste defined by age group

each caste has distinct physiology and hormonal basis

hormones control differential gene expression between castes

Throw away caste hypothesis (Amdam et al)

• foragers only live a short time

• no point investing in forager immune system

• foragers should adaptively down regulate their immune system

Evidence for throw away caste hypothesis

foragers have lower:

• antioxidants

• white blood cells

• gene expression of AMP

BUT never actually measured immune system properties

Throw away caste hypothesis Follow up experiments

• infected nurses and foragers with various pathogens

• measure survivorship, gene expression, and metabolic activity

• found foragers actually have strongest immune system

• Foragers are not expressing AMPs because they already have antimicrobial proteins

Throw away caste hypothesis Takeaways

using simple proxies instead of measuring the actual variable can lead to mistakes. Although the proxy (low white blood cell count, low gene expression) are usually indicative of low immune function, they do not prove it. In is necessary to test the real response

Evolution

change in biological systems over time

3 drivers of evolution

• natural selection (adaptation)

• Drift (random changes)

• major random events (eg major geological events)

Natural selection criteria

1- variation

2- heritability

3- differential reproductive success

continuous variation

variation curves (eg height, weight)

discrete variation

noncontinuous traits (eg flower color in mendels peas)

sources of variation

• mutation

• sexual reproduction (recombination)

heritability

offspring resemblance to parents

genetic inheritance

differential reproductive success

increased fitness of certain individuals

Sexual selection

competition for obtaining mates (natural selection in reproductive context)

Convergent evolution

similarity due to similar selective pressures

analogous similarities

homologous similarity

similar by common descent

systematics

process of building evolutionary trees

shows the pattern of divergence among groups of organisms

methods of tree building

older methods based on morphology

new methods use similarities within DNA

Levels of analysis (Tinbergen)

• origin

• current utility

• developmental origin

• physiological genetic mechanisms

Tinbergen levels of analysis: Why do birds have feathers?

• origin: to keep warm

• current utility: flight and warmth

• developmental basis: genetic pathways

• physiological genetic mechanisms: ?

Early insect systematics

most were wrong bc they were based on morphology

convergent evolution caused mismatches

closest relatives to insects

crustaceans, then myriapods, then chelicerates

outgroups to insects

Remipedia

• found in salty aquifers

• small venomous predators

Brachiopoda

• water fleas and fairy shrimp (mostly eat detritus)

• brine shrimp (commonly used as fish food)

these crustaceans are more closely related to insects than to other crustaceans

Earliest insect fossils

412 mya

Likely insect origin

450-409 mya

progression of insect evolution

insects and plants coevolved

scavengers, then herbivores, then predators

types of traits

behavioral, anatomical, molecular (any aspect of an animals biology)

antibiotic resistance example

1- group of bacteria is exposed to antibiotic

2- most of normal bacteria die

3- genetically resistant bacteria start multiplying

4- resistant strain replaces normal strain

Invertebrates

no backbone

functional group (defined by common traits, not evolution)

functional group

group defined by traits rather than evolutionary history

functional groups can often be more useful in ecology

monophyletic group

group that shares a common ancestor

Major classes of arthropods

• Arachnids (spiders mites, ticks, scorpions)

• Crustaceans (crabs, shrimp)

• Chilopods (centipedes)

• Diplopods (millipedes)

• (chilopods and diplopods make up myriapods)

• Hexapoda/Insecta (insects)

Insects (what traits define an insect?)

• exoskeleton

• jointed legs

• segmentation

• ventral nerve cord

• dorsal blood vessel

number of body segments for each type of arthropods

• Insects: 3 segments, 6 legs

• Arachnids: 1 or 2 segments, 8 legs

• Crustaceans: 3 segments, variable no. of legs

• Centipedes: 15 segments, 30 legs (one pair per segment)

• Millipedes: 11-100 segments, 30-750 legs (two pairs per segment)

Groups within Hexapods

• Collembola (springtails)

• Protura

• Diplura

• Insecta

Zygentoma

• fire brats, silverfish

• wingless

• no metamorphosis

• mostly scavengers

• some are pests

• few hundred species?

Zygentoma (silverfish, fire brats)

Odonata

• dragonflies, damselflies

• about 5500 species

• fixed wings

• aquatic predators as juveniles

• flying predators as adults

Odonata (dragonflies & damselflies)

Mayflies

• about 3000 species

• fixed wings

• mainly aquatic herbivores

• two molts (subimago, imago)

• adults are very short lived (dont feed, mate and die)

• can be very abundant for a short period of time

Mayflies

Dermaptera

• Earwigs

• about 2000 species

• hemimetabolous (incomplete metamorphosis; juvenile looks like adult)

• Mostly scavengers (some predators/ herbivores)

• Most have parental care

Dermaptera (earwigs)

Orthoptera

• crickets, grasshopper, catydids

• hemimetabolous

• about 27,000 species

• all herbivores

• model system for many aspects of reproductive biology

Orthoptera (crickets, grasshoppers, catydids)

Mantodea

• praying mantises

• about 2500 species

• all predacious

• many have camoflage

Mantodea (mantises)

Insect circulatory system

The insect circulatory system does not transport oxygen and is not a closed system, so it is low pressure

Distributed nervous system

Many small brains instead of one; each system can function on its own

How do male mantises continue mating after death?

Open circulatory system; distributed nervous system

Phasmatodea

• walking sticks

• about 3000 species

• hemimetabolous

• strict herbivores( make their own cellulases)

• highly camoflaged

• often toxic

Phasmatodea (walking stick)

Blattodea

• roaches and termites

• about 4500 roach species

• about 300 termite species

• hemimetabolous

• most are not pests

• omnivorous

Blattodea (Roaches and termites)

Thysanoptera

• thrips

• about 6000 species

• hemimetabolous

• tiny sucking insects (both predators and herbivores)

• some vector plant diseases

Thysanoptera (thrips)

Hemiptera

• true bugs

• about 75000 species

• all have piercing and sucking mouthparts

• includes many common predator and herbivore groups (aphids, leafhoppers, kissing bugs, cicadas, scales, etc)

• many pest species

Hemiptera (true bugs)

Neuroptera

• lacewings

• holometabolous

• mostly predacious insects (as juveniles and adults)

• some look like flying mantises

• many brightly colored

Neuroptera (lacewings)

Mecoptera

• scorpion flies

• not flies but part of a clade including flies and fleas

• about 600 species

• studied for elaborate mating biology

• holometabolous

Mecoptera (scorpionflies)

Hymenoptera

• sawflies, wasps, ants, bees

• more than 150000 species

• most primitive group are herbivores (sawflies)

• most species are parasitoids

• all have ovipositors (aculeates have modified ovipositor that is a stinger)

• includes most highly social insects

Hymenoptera (wasps, bees, ants)