Biology 12 Laboratory

R.S. Gonzales, Ph.D.

Institute of Biology, UP Diliman

Levels of Ecological Study

Ecology of Individuals

Foraging involves decisions regarding the

allocation of time and energy

Principle of Allocation – If energy supply is limited, organism must compromise between competing demands for energy (growth and reproduction vs. defense)

Optimal foraging theory

Hypothesis: natural selection should favor efficient foragers, those individuals that maximize their energy or nutrient intake per unit of effort.

Foraging: what food to eat; where and how long to search; how to search.

Costs and benefits Cost: time and efforts on foraging

Benefit: survive and reproduce more, fitness

Optimal foraging by ants

Rockwood & Hubbell 1987

Using Optimal Foraging

Theory to predict composition

of animal diet

Bluegill Sunfish (Lepomis

macrochirus)

• Studied by Werner &

Mittelbach (1981)

• Medium-sized freshwater fish

native to eastern and central

North America

• Feed mainly on benthic and

planktonic crustaceans and

aquatic insects

• Choose prey by size

Population Ecology

Morisita’s Index of Population Dispersion

~ 1 = random

~ 0 = uniform

> 1 = aggregate/clumped

Patterns of dispersion

Random Uniform Clumped

Neutral interactions

among individuals

and between

individuals and the

environment

Antagonistic interactions

among individuals or

local depletion of

resources

Attraction among

individuals or

attraction of

individuals to a

common resource

Population Growth Models Per capita population growth rate (r) per capita

birth rate minus per capita death rate

Intrinsic rate of increase of a population (rmax) maximum population growth rate under ideal conditions

Carrying Capacity (K) The maximum population size that an environment can support indefinitely.

r-strategists vs. K-strategists

Aspect r-strategist K-strategist

Maturation time Fast Slow

Life span Short Long

Mortality High Low

No. of offspring per

reproductive episode

Many Few

No. of reproduction per lifetime Once or few Often several

Timing of 1st reproduction Early Later in life

Size of offspring Small Large

Parental Care Absent or little Present

Environment Harsh, unstable Stable

Example Fruit fly, grass Man, trees

Ecology of Interactions

Intraspecific and Interspecific

Competition

What is competition?

Negative interaction between 2 organisms that

utilize the same resources

Intraspecific vs. Interspecific

competition

Interspecific –

between different

species

Intraspecific –

between the same

species

Ecological Niche

The ecological niche of a species

includes its habitat, role in the

community, and its position in

environmental gradients of temperature,

moisture, pH, soil and other conditions

of existence.

Competitive Exclusion Principle –

“complete competitors cannot co-exist”

Competition and the

Ecological Niche

1. Niche separation

2. Habitat shift

3. Character

displacement

4. Competitive

exclusion

5. Competitive release

Spatial and Temporal Partitioning

Allelopathy – “other suffering”

Plants secrete substances that are harmful to

other species to avoid interspecific competition

Stand of Mahogany

trees, which are

exotic species

introduced in the

Philippines (note the

absence of other

species that coexist

in the same area)

Community Ecology

Vegetation Analysis

What is species diversity?

The number and distribution of species in

a community

species richness – total number of species

per unit area or in a population

evenness – number of individuals of each

species per unit area or in a population

Which is more diverse?

Sp. Richness 4 4

Community Sp. A Sp. B Sp. C Sp. D

1 5 5 5 5

2 17 1 1 1

Diversity Index

Simpson’s index

Where n = total no. of indivs in each species

N = total no. of indivs in all spp

𝐷𝑆 = 1 − 𝑛𝑖 (𝑛𝑖 − 1)

𝑁(𝑁 − 1)

Similarity Indices

𝐶𝐶 = 2𝑐

𝑠1 + 𝑠2

Where c = no. spp. common to both communities

s1 & s2 = no. spp. found in community 1 and 2, respectively

𝑃𝑆 = 1 − 𝑝𝑖 − 𝑞𝑖

2 × 100

Where pi = proportion of different species in community 1

qi = proportion of different species in community 2

Ecosystem Ecology

Primary

Productivity

Gross primary production

– total amount of biomass

produced by all the

autotrophs in the ecosystem

Net primary production

– amount of biomass left

over after the autotrophs

have met their own

energetic needs

Plants as the Base of the Food

Pyramid

Herbivores remove between 15 and 18% of

terrestrial plant biomass and over 50% in

aquatic systems

Kinds of Food Pyramids

1. Pyramid of Numbers

2. Pyramid of Biomass

3. Pyramid of Energy

Kinds of Food Pyramids

1. Pyramid of Numbers – based on total count

of individuals

Kinds of Food Pyramids

2. Pyramid of Biomass – based on total weight of

individuals

Kinds of Food Pyramids

3. Pyramid of Energy – based on total productivity of

individuals

1o productivity

2o productivity

Ecosystem Ecology

Microclimate: Aquatic

Temperatures

Relative Humidity (in %)

Absolute Humidity – water content of air

Relative Humidity = Actual vapor pressure

Saturation vapor pressure

AVP amount of water vapor in air

SVP maximum water vapor air can hold

inversely proportional to temperature

Indicator of the chance of rains. In hot summer weather, a rise in relative humidity increases the perceived temperature

Salinity Oceans have average of 36.5 ppt

Rivers have < 0.1%

Dissolved Oxygen

> 9.0 ppm supports abundant fish

< 5 ppm is stressful for most fish

< 3 ppm is too low, even hardy fish die

Plants – produce oxygen during

daytime, but use it up during nighttime

Relationship between Abiotic

Factors in Freshwater Ecosystem

Velocity of water flow DO

Light intensity DO (up to a certain point)

Water temperature DO

Light intensity pH (up to a certain point)

DO pH

α α

α 1/ α

α

Evolution

EVOLUTION

Evolution is the change in genetic composition of

all life forms over generations.

It is commonly described as “descent with

modification”.

The central idea

of biological

evolution is that

all life on earth

share a common

ancestor.

Mechanisms of Evolution

Mutation

Migration

Genetic Drift

Natural Selection

MECHANISMS

MUTATION

http://learn.genetics.utah.edu/archive/mutations/index.html

At conception, permanent changes in the

DNA sequences of genes may occur.

MECHANISMS

MIGRATION Two populations having different gene

frequences can interact. This interaction will

cause the gene frequencies to unify.

http://www.blackwellpublishing.com/ridley/a-z/Migration.asp

MECHANISMS

GENETIC DRIFT Changes in the frequencies of an allele in a

population due to random sampling.

http://www.sciencedaily.com/articles/g/genetic_drift.htm

MECHANISMS

NATURAL SELECTION Individuals with certain heritable traits survive and reproduce

better than the others. Over time, natural selection can increase

the match between organisms and their environment.

http://evolution.berkeley.edu/evolibrary/article/evo_25

DARWIN’S OBSERVATIONS 1. Organisms beget like organisms

2. There are chance variations

between individuals in a species.

Some variations are heritable

3. More offspring are produced each

generation than can be supported

by the environment

4. Some individuals, because of

their physical or behavioral traits,

have a higher chance of surviving

and reproducing than other

individuals in the same population

TYPES OF

EVOLUTION

MACROEVOLUTION

Development of new species due to accumulation

of changes over a very long period of time.

MICROEVOLUTION

Changes obseved in every generation of organisms.

EVIDENCES OF

EVOLUTION

FOSSIL RECORDS

EVIDENCES OF

EVOLUTION

HOMOLOGOUS STRUCTURES AMONG

ORGANISMS OF DIFFERENT SPECIES

EVIDENCES OF

EVOLUTION

MOLECULAR HOMOLOGIES

EVIDENCES OF

EVOLUTION

ORGANISMS THAT ARE ADAPTED TO

THEIR ENVIRONMENT

Types of evolution

1. Divergent –organisms having a single ancestor

take separate pathways of evolution, resulting in

different groups

Homologous structures

Types of evolution

2. Convergent – different groups of

organisms that do not share common

ancestry take similar pathway of

evolution due to similarity in the

environment they live in

Analogous structures

Comparing primate skeletons

Gorilla Australopithecus Homo sapiens

Brain case, temporal area, and brain sizes

Crest prominence

Brow ridge

Degree of facial protrusion

Size of pelvic opening

Brain size

Humans have much

larger brain; capable

of language,

symbolic thought,

and the manufacture

and use of complex

tools

Sagittal crest

ridge of bone running

lengthwise along the

midline of the top of the

skull of many

mammalian and reptilian

skulls, among others.

presence indicates that

there are exceptionally

strong jaw muscles

Supraorbital ridge

brow ridge functions

to reinforce the

weaker bones of

the face

necessary when

there is tremendous

strain put on the

cranium by powerful

chewing

apparatuses

Facial Protrusion More protruded lower facial

area indicates greater

dependence on sense of

smell

More flattened face

indicates greater

dependence on sense

of sight

Pelvic opening and the

“Obstetrical dilemma”

Two conflicting trends:

1. Upright, bipedal locomotion required

decreased size of bony birth canal

2. Increased intelligence required larger cranium,

which needs a wider obstetrical pelvic area

Humans have more difficult time giving

birth

Shorter gestation length, babies with

malleable skull and underdeveloped brain

Our species Homo sapiens is only 200,000 years old

Derived Characters of Humans bipedal locomotion

much larger brain; capable of language, symbolic thought, and the manufacture and use of complex tools

reduced jawbones and jaw muscles

shorter digestive tract

*Humans & chimpanzees have genomes that are 99% identical (but they differ in the expression of 19 regulatory genes)

Humans: Mammals with a Large

Brain and Bipedal Locomotion