Adaptive or Functional morphology - Autecology

What is the origin of our morphologies or how do

structures work

• (Palaeo)Autecology: study of the life modes of organisms and the relationship between individuals and the environments. It focusses on the growth and shapes of organisms ad on the correspondence of morphology to both life strategy and habitats.

Aims:

• To define the function of a particular anatomical form

• To describe how organimsms reached their present forms.

Phases:

(1) God’s luck: Divine designer(2) B. G. Cuvier: the founder of comparative anatomy(law of correlation parts)

(3) C. Darwin• Adaptation: accordance between an organism and the

environment or it is the fitness of an organism to its environment

Anatomical form = Morphology

Influential factors

• Our morphology (adaptation to environmental needs) is interrelation of the following factors :

1) the genome; 2) the development of body plan (isometric growth vs. allometric growth)

Growth strategy: the development of body plan

• Marginal accretion: adding on discrete growth layers to their skeletons as they get larger; leaves "growth lines"

• Addition: discrete new parts added or intercalated, with little change afterward

• Adding body segments

Serial addition

• in colonial organisms: the parts replicated are comparable to entire other organisms

Molting

• each growth stage or instar is entirely new hard part material; allows for radical transformation between growth stages

(extreme in advanced insects); leaves discrete size classes representing age

classes.

Continous modification

• Bone tissue remodelled throughout ontogeny.

Influential factors

3) the function of the organism; 4) the organism’s behaviour

Investigative methods

• Structure can be compared directly with modern, working counterparts (homologues, analogues).

• Paradigm approach: one function can be tested against the efficiency of a mathematical or physical model for the working structure

• Application of various experimental techniques where physical models are subjected to simulated encironments.

1. Experimental palaeoautecology

2. Computer simulation

Procedure

Each structure has to be describe.Described structures are compered one to another and to the environment.

Function and morfology for each structure has to be define.

Connection between structural performance and fitness to morphology.

Analogues and homologues

• The morphology ad function of a modern structure is compared with an assumed counterpart in an extinct or fossils organism.

• Homologous structures, like wings of birds or lungs of the vertebrates, have evolved once.

• Analogous structures: evolved at different times from different structures (wings in birds, in insects…

Analogues and homologues

• Could exist does exist?• Certain morpholohy repeats over Life

evolution: Some adaptations are mechanically advantageous and easy to produce developmentally

Convergation

• Different lineages of organisms can independently develop some of the same features, even though ancestors were quite different (e.g., streamlining in sharks, tunas, ichthyosaurs & dolphins; cactus-like form in separate lineages of plant; etc.).

How this method works in the field?

• We have to define the adaptation or the structure we pick up for study, then make a list with all organisms that show this adaptation or have this structure – Theoretical and traditional morphology

• Try to go far in the past to see who was the first organism that showed this adaptation or had this structure - phylogenetic lineages in order to see wh this adaptation/structure arose

• Ancestor and descendants form a lineage (historical line). If the same basic adaptations are selected for and elaborated over time, this is called a trend. (e.g., longer and longer legs for fast running; longer and longer necks for browsing in trees, etc.)

• If a new adaptation (or loss of competitor group) occurs, many different variations from a common ancestral population might survive (new or unoccupied "niches" in environment). Over a geologically short period time, a common ancestor can radiate into many different descendant lineages

Paradigm approach

• The aim to bring scientific methodology to functional studies

• First we have to postulate one or more bilogical functions for a particular structure

• Secondly for each function an ideal model or paradigm has to be designed

Case study: gastropods

• We study the following prameters: shell’s shapes, aperture’s shape; apex, number of whorl, ornamentation…

Shapes

• Ratio between measurable parameters define the shape of shells.

Height > Width Width > Height

Aperture shapes

Moonlike Rounded

Kiddney-like

Apex

• α<300 α=150-1800 α= 60-900

Number of whorls

n < 4 n = 6 – 10 n > 10

Ornamentation on the last whorl

Smooth surface Growth line

Costa

Costa

Case study: gastropods

• We study, also: axis of coiling; expansion rate (W), Distance from the generating curve (D), Translation rate (T)

Mathematical model, X-ray image and real mode help us to measure the

parametersl

W D

T

Mathematical model

• The variation in the form of planispirally coiled cephalopods summarized by varying expansion rate (W) and distance of aperture from axi (D)

W

Paradigma ‘s bad characteristics

• Structural constrains: usually special puropese for each structure! Not necessary

• Evolutionary heritage: an organism can build a new anatomical feature only out of the raw materials that were furnished by its ancestor.

• Pleiotropy: single gene has many independent phenotypic manifestation.

• Ecophenotypic • Organisms of the same species may

look substantially different depending on their environment, e.g. Scleractinian corals in different energy regimes.

• There may be no selective advantage whatsoever (human chin)

• Not every feature is optimally designed

• The correlation between structure and function is not perfect

Computer simulation

Adaptation

• How well an organism is fitted to its environment?

• Size as an adaptation

• What do you think: are large organisms better adatped than small ones?

• Giants are particularities of the certain groups of organisms. Is it simply chance, or are there biomechanical reasons?

• Why do some groups never produce giants?

• Does evolution always go from small to large? Cope’s law

• How long does it take for large size to evolve?

• What is better: to be giant or to be dwarf?

Biomechanical reasons or constraints

• Mechanical postulates are adopted for analysis of organisms.

• Investigations are directed towards:• Toughness of the matter and

architectural pattern• Energy and power: Prey and

mandible• Motion: swimming, flying, propulsion

Biomechanial reasons

Why so few giants?

• Arthopods would suffer the cost of moulting dozen of times

• Filter-feeding habitis of brachiopods, most molluscs, bryozoans, graptolites, some echinoderms because exposed cilia cannot sustain a large organism.

• Mechanical constrains in shells: weight of shell and the amount of calcium carbonate to be extracted from the sea-water tend to prevent huge size.

Time necessary for development of giants – Evolution of large size

Triassic (Norian) – Prosauropodi (Plateosurus), 5m = body length

Liassic – Melanosaurus12 m = length, weight = 10 t

Time necessary for development of giants

• Bathonian – Kimeridge – the largest dinosaurs up to 30 m in length, weight = 80 t

Advantage and disadvantage of large size

1. Improved ability to capture a prey or escape from predators

2. Greater reproductivity success3. Increased intelligence4. Better stamina5. Expanded size range of possible food items6. Decreased annual mortality7. Extended individual longevity8. Increased heat retention per unit volume

Advantage and disadvantage of large size

• Greater proneness to extinction 1.expression of specialization: need for

large amounts of food and, need for particular environmental conditions

2.small population sizes i.e. small gene pools)

Heterochrony

• Changes in the developmental rates of an organism

• Result: set of growth strategies that produce significant morphological changes between parent and daughter populations.

Paedomorphosis

• change in which the adult of a derived organism resembles a juvenile of the ancestor.

Peramorphosis

A juvenile of a derived organism resembles an adult of the ancestor. Ancestor

Descedant

Sexual Dimorphism

• Male and female organisms of the same species differ a lot.

How do we distinguish dimorphismsin fossils?

• Analogy with living relatives• Ratios of presumed females to males

(differentiation in size, shapes...)• Taphonomic variability: post mortem

distortion